While the United states became increasingly embroiled in Laos and Vietnam, mounting pressure was being brought to bear on the British Government, as a signatory of SEATO, to go to the assistance of its allies, but this pressure was with equal force resisted in Whitehall. In December 1962 however,the Prime Minister, in anticipation of a meeting with President Johnson, wished the U.K. to be seen to be playing some part in stemming the march of Communism on the mainland of Asia without, if possible, becoming involved in the actual fighting. The Americans were then simultaneously engaged in a massive programme of Special Logistic Aid to Thailand (SLAT) and a U.K. participation in this might be acceptable as a token of Allied solidarity, this participation was accordingly put to C- in - C Far East Command.
As the work in North Borneo was then all but practically completed and the revolt in Brunei had not yet erupted, the advent at this time of SLAT was welcomed in FARELF as a potential fruitful field for further endeavour, offering opportunities to gain valuable experience and favourable publicity for the Services. of the schemes examined by the Chief Engineer FARELF, the construction of an entirely new MTR airfield for use by SEATO forces appeared to be the most attractive. The site was at Leon Nok Tha, near Mukdahan. It was close to Thailand's eastern boarder with Laos and some 70 miles north of an existing rail/air head of Ubon Ratchathani.
In February 1963 this proposal was submitted to Whitehall and came to realisation under the name of Operation Crown. Authority to conduct even a preliminary reconnaissance was, however, delayed, awaiting Thai Government authority, until May 1963, by which date the coming dry season (Sept - April) was uncomfortably close and, more significantly, the situation in Borneo has deterioated, drastically reducing the availability of men, machines and transport. it was, notwithstanding, agreed to produce a team led by CRE SLAT, with a representative of FEAF Airfield Construction Branch, visited the site and quickly produced in very adverse weather conditions a proposed design, along with a rough estimate of £600,000 for an airstrip 5,00 feet long and 120 feet wide with 500 feet overruns 90 feet berms along with 1million square feet of associated apron and parking space.
More extensive reconnaissance was prescribed for fear of prejudicing the negotiations in which HM Ambassador in Bangkok was simultaneously engaged with the Thai government regarding their contribution to the cost of the works, so the CRE - designate was constrained to make his early plans on incomplete information and, at first, with no staff. at last, at the end of November, authority came from London to go ahead and CRE FARELF could release his first Engineering Operation Instruction. Conveniently, the completion of the Commonwealth Cantonment at Terendak had by then thrown up the establishment for CRE (Works) FARELF, which was promptly appropriated to this project and, with effect from 1 January 1964, renamed CRE Crown.
It had hitherto been envisaged that one Field Squadron would be employed to set up camp and be followed by another with plant and administrative support to build the airfield and the whole project was to be completed over two dry seasons bu June 1965. Owing, however, to the delay in starting and the approach of the rains in May, it was resolved to double the initial effort in Thailand with the consequent large addition to the accommodation and logistic requirements there. This turn of events had the effect indirectly of securing for Borneo much needed and long overdue reinforcements which, though repeatedly asked for from UK, had hitherto as often refused. Meanwhile in December 1963, an advance party of CRE Crown was deployed to Mukdahan to begin detailed site investigation work, in particular, to locate construction materials and do a detailed survey of the runway alignment, pre-requisites for confirming or revising the findings of the preliminary reconnaissance team.
At the same time, leading elements of 11 Field Squadron established a tented camp on the airfield site. I January they were joined by the rest of the squadron (including its attached troop of RAE), followed by plant from 54 Corps Field Park Squadron, newly arrived from UK. Machinery was meanwhile brought up from Singapore by sea to Bangkok, whence it was forwarded by rail and road, which necessitated the strengthening of some of the bridges on the route. Air maintenance, limited because of operational demands from Borneo, was from then on to be a containing constraint of the movement of men and of urgently needed stores.
The main effort to begin with was applied to the construction of roads, a helipad and a hutted camp for the workforce. Water for the works was from the outset a recurrent problem and at one time had to be hauled from a distance of 18 miles. By April the camp was ready for occupation an 11 Squadron could be release, the plant working two shifts a day, had cleared the alignment for the runway and removed top soil to an average depth of two feet to reach sand suitable for cut and fill operations to form the sub grade, clay in the sub grade being replaced by sand. The ground was extremely dry and the whole area became covered with dust, making it unpleasant work in shade temperatures up to 110 degrees Fahrenheit (40c). progress at this point was well ahead of schedule, but operations were being increasingly interrupted by un-seasonal rains and, at the end of May, earthmoving was suspended. Water supply had, for the time being, ceased to be a problem. In July, after completing a temporary strip for light aircraft, 59 Squadron returned to Singapore for a period of rest and re-training.
The initial design for the airfield produced by CRE SLAT in June 1963 was for a wearing surface of Pierced Steel Planking (PSP) on a base of compacted laterite and sand, 18 inches thick. The top three inches of the laterite were to be stabilised with bitumen to produce a waterproof seal to the pavement. The findings of the more detailed investigation carried out by CRE Crown technical team from January to June 1964 led to a re-design of the runway pavement. It was found that the locally occurring laterite, apart from being much less extensive than expected, contained a high proportion of clay. This rendered the material unsuitable for bitumen stabilisation. Also, there were second thoughts about the use of PSP. The Americans had experienced difficulty with a nearby airfield at Nakhon Phanom surfaced with PSP, where the metal cut through the waterproof seal. There was also concern that PSP was unsuitable for the higher tyre pressures being used on modern aircraft and a worry about the effect of the metal on electronic equipment. Revised designs were develo0ped by CRE Crown and a final proposal submitted in October 1964 - was well into the second dry season of the project - was for a surface of two inches of bitumen macadam on a base of six inches of stabilised laterite, upon a sub-base of compacted laterite and then sand, giving a total pavement thickness of 22 inches. It was proposed that the base stabilisation should be done using both lime and cement and this method was endorsed by the Road Research Laboratory in the UK. The pavement design was approved by the Chief Engineer FARELF and financial approval for an extra cost of £38,500 was given by the Treasury in November.
Meanwhile in August work had been resumed on site, six full days a week, now hindered once more by an acute water shortage and by breakdowns in the whole range of ageing plant. Because some of the materials had to be collected from sources as much as 200 miles distant, when stabilisation began it was sometimes impossible to keep more than one of the four Howard trains in action. However, the runway base was finished by the end of March, and the macadam surface by the end of May, when the New Zealand detachment was withdrawn. Determined efforts to beet the monsoon enabled the control tower, airfield fencing and lighting to be completed in time for the opening ceremony to be preformed on 17 June 1965 by the Thai Minister of Defence in the presence of his Prime Minister and the British Ambassador. It was now apparent that the cost would overrun the approved estimate by a substantial margin and, furthermore, it would scarcely be possible to complete the outstanding works and evacuate the site by the planned date, 31 October 1965. More alarmingly, it was soon apparent that the airfield was showing signs of failure, with soft patches and rutting.
In October 1065, Colonel Engineer Plans (Airfields) in MOD visited Leong Nok Tha to investigate what residual work was required to reinstate the pavement. In doing his investigation, he identified the most likely causes of failure.
The main reason he found was the porosity of the bitumen macadam. This, coupled with an inadequate cross-fall, allowed water to be retained as if in a sponge, from whence it filtered down through cracks and imperfections in the stabilised base to soften the laterite sub base below, sufficient to cause failure. With the benefit of hindsight, it is possible to catalogue many contributing causes for the failure. For reasons of economy, the bitumen macadam was very much a marginal design. It could have worked, but the aggregates used were of poor quality due to local circumstances and the mixing plant was to old and inadequate for the task. The result was a macadam that looked fine when laid but which "stripped" (bitumen aggregate adhesion failure) when wet. The in adequate cross-fall accentuated the problem. The stabilisation generally worked well, but there were many problems with equipment serviceability, no compounded by the remote location and operator experience. There were doubts too about the quality of the local cement. It was expected that there would be minor imperfections in such stabilised bases and a waterproof seal was essential. The laterite used for the sub-base was of a very variable quality, comprehensive laboratory testing had indicated a reasonable bearing capacity for this layer, but in the event, the material as laid proved far weaker. Desirable field trials could not be carried out because of time constraints, the percolating water guaranteed failure.
Pending the outcome of technical enquiries, the whole question of SLAT and of Crown in particular, came under review at high level, with certain circles in Whitehall pressing for a decision to cut the losses and clear out of Thailand as quickly as possible. This un soldierly proposition was, however, most strongly resisted by the E-in-C, contending with eventual success that, quite apart from political and military considerations, the Royal Engineers should be allowed the opportunity to retrieve their fortunes, to regain confidence in themselves and to restore their reputation in the eyes of the RAF. This latter was particularly important as the assumption of responsibility for airfield construction by the Royal Engineers from the RAF was at its hight at the time.
In November 1965 11 Field Squadron took over from 59 Field Squadron the ongoing works, while the latter moved back to Singapore for re-training. Meanwhile, a new batching and mixing plant was ordered and brought up in time to be taken into use by 59 field Squadron on their return in May 1966. The resurfacing sequence involved stripping back the blacktop, ensuring that the underlying stabilisation was intact, or repairing as needed, and then placing an 8 inch layer of pavement quality concrete (PQC). in this phase, the force found itself fully stretched with two concreting parties working alternate 8 hour shifts with others employed on associated and secondary tasks, which included laying blacktop shoulders,re-turfing, runway and taxiway markings, cutting and sealing joints in the pavement, besides normal camp services and administration. The task was, notwithstanding, all but complete by October when 59 Squadron had to be taken off the project to assume its new role in support of 3 Commando Brigade, Royal Marines. By then 11 Squadron was engaged elsewhere, including Vientiane in Laos whither a detachment has been sent to assist in flood relief operations.
The confrontation in Borneo was, however, then seen to be coming to an end. 34 Field Squadron, which has arrived in Singapore in September from the UK was to be deployed there, was deflected to Thailand to finish the work. When, in December 1966, the reconstructed airfields was finally proved and handed over, CRE Crown was dissolved, some of its staff going to join the HQ of CRE (Ops) FARELF and the establishment cover being transfered to 63 CRE (Construction), which opened in Singapore in January 1967. Thus ended the not altogether happy saga of Leon Nok Tha. With so little by way of preliminary investigation, the bold decision to proceed was from the start fraught with risk yet, the risks most feared were - as is often the case - not the those that materialised, while the circumstances which led so nearly to failure were at once unpredicted and unpredictable. In the event, no lasting damage was done, for, as the operation neared its end, negotiations were already underway with the Thai Government under which a similar workforce was to remain for a further year to undertake, under the code name Post Crown, road construction.
The original suggestion made in September 1966 to the Thais was that a road should be built North West of Loeng Nok Tha to a village some 25 kilometres away called Ban Khok Klang. Such a road would provide access in all weathers for several hitherto isolated communities, while at the same time contributing materially to the internal security of an area open to communist incursions from across the nearby Mekong river. the Thai Government agreed to pay for and deliver to the site all construction materials, and provide civilian labour, the British were to provide plant and project control staff. The alignment - after several revisions - was finally fixed in November and work started in earnest on 2 January 1967.
The initial target of 25 kilometres had been fixed largely because it had been assumed that the force would have to leave Thailand at the end of 1967. However, in August it was agreed that the British could remain until 1 May 1`968 to extend the road westward from Ban Khok towards Nong Phok, some 14 kilometres away, if the Thais extended their existing road from there eastward to meet them. In the event, the link was completed by a combined British and Thai force, under British command, working west. Control of the project was exercised under CRE (Ops) FARELF by each OC of the squadron deployed to the task at any one time, who had additional staff including a Thai liaison officer and the FARELF Air Troop RE in support. The main base camp remained at the Crown site, with a forward construction camp at Hong Khong.
34 Field Squadron, having completed its task on the airfield, began work on the road in December and was relieved by 59 Field Squadron in May 1967. In August they were relieved by 11 Field Squadron who bore the brunt of the monsoon. By the end of December - when the original 25 kilometres of road would have been finished - no other unit was immediately available at hand to continue the rotation. Accordingly, from January 1968, a composite workforce made up from a 54 (FARELF) Support Squadron and one troop each from 51 (Airfields) and 59 Field Squadrons, took over and, with the Air Troop RE still overhead, brought the extended project to completion
The 40 kilometre long road was formally declared open on 18 April 1968. An impressive ceremonial was mounted by 54 support Squadron marching past in white No. 3 Dress and comparing favourably with a smart detachment of the Royal Thai Army brought in for the occasion.
Since the people of Leong Nok Tha had virtually no experience of operating or maintaining any form of machine, the development of water supplies in the surrounding villages began with the provision of hand pumps drawing from shallow wells but, towards the end , a start was made to introduce a more advanced system, putting down 200 feet deep wells, with eclectic pumps powered from diesel generators, in association with limited piped distribution and water towers built by the villagers themselves. in this and in other directions training the local inhabitants turned out to be a rewarding by-product. Some of them quickly mastered the procedure for setting out. unsupervised, straightforward sections of road alignment. The 15 bridges (some of five or six spans) were built by teams of two Sapper carpenters and 12 Thais, and the 1,700 reinforced concrete pipes required for the 93 culverts were manufactured entirely by villagers under the supervision of s Sergeant of the Thai Army. up to 200 were engaged to work on the road, not all on unskilled tasks. Numerous subsidiary projects were carried out by the Sappers - not infrequently in their off-time - with the grateful cooperation of the local populace, before the last of them left the district in November 1968.
The friendships forged at Leong Nok Tha blossomed into yet another programme of projects in another part of the country. In October 1969, an ad hoc Specialist Team RE (Thailand) under 63 CRE (Construction) was formed. A combination of geological, political and administrative considerations led to the STRE being based at Chm Bung, near Rat Buri and some 50 miles from Bangkok, where it was occupied principally with well drilling and water supply installations, but also building schools. By the time its programme had been completed in September 1971, the team had drilled eight wells, the deepest of which was 236 feet.