It is important to understand how these three cemeteries came into being. Of them, only ChungKai was an actual wartime cemetery. It was thought that many of those currently buried there actually died at the hospital that operated at that location after construction work in that area was completed. It was a convenient place for a hospital. It was reasonably separated from the nearby city and IJA HQ at Kanchanaburi but yet accessible. Survivor accounts tell us that barges returning to the city after a supply delivery would often ferry the sickest of the POWs from the up-country camps. ChungKai is on the direct route back to the city. But a substantial number of those buried there are recorded as dying in other places. So the story of hospital deaths is not exactly true. It must also be noted that of the 311 Dutch burials there we have no recorded CODs nor location of death. Obviously, the vast majority (82%) of all POW deaths occurred during the construction in 1943. One interesting item is that almost all of the 1944-45 burials at ChungKai were Dutch. There are also no Australian graves here. This, too, would tend to discredit the died-there, buried-there theory.
[See the footnote for an explanation of these late burials]
The graves at Thanbyuzayat are those of POWs who died in the Burmese Sector of the Railway. This is complicated, however, by the large number of deaths among F Force members who were evacuated to a special camp established at Kilo 50 (Thambaya). The majority of the POWs who worked in Burma were Dutch and Australian as well as the over 600 US personnel. IOW, there were very few British. This stems from the fact that the Burmese Sector workers were captured on Java which included relatively few British personnel. The small group of British who worked this sector arrived from Sumatra.
In the latter stages of the construction, there seems to have been a mingling of groups of workers just inside the Thai border. This was technically still the under the control of the 5th Railway Regiment. Most of the work force from Burma had made its way into Thailand by Sep-Oct 1943 as construction was about to be completed. At this same time, parts of F Force were arriving in that area. As conditions among F Force deteriorated to the point of an emergency, many (including thousands of British) were evacuated to the Kilo 50 hospital camp; of whom 500 were known to have died there. Many more died in the camps near the Thai-Burma border. Eventually, those remains were gathered at Thanbyuzayat. This then accounts for the larger than expected number of UK graves at Thanbyuzayat. F Force was reportedly about 50% Australian, but since we have few COD records for them we do not know if they were present in these same camps that suffered such a heavy death toll. Perhaps they had been allocated to other camps as the march proceeded.
Something of the opposite circumstances resulted in many of those who had worked in Burma being buried at Don Rak. After completion of the Railway, all the POWs were consolidated to the camps in and around the city of Kanchanaburi. Men continued to die of conditions contracted earlier well into 1945. With the exception of malaria which was encountered everywhere, almost none died of conditions contracted after the completion date of OCT 43.
Here are the generally accepted figures for where the various POWs worked by nationality as well as the distribution of graves:
I have included my estimation of where the 131 US personnel would have been interred based on what we know about when and where they died.
Looking at the registered CWGC graves by the location we have nearly 6800 at Don Rak, 1700 at ChungKai, and 3600 in Burma. But, respectively, the number of CODs aligned to those are 2700, 700 and 1400. Those figures calculate out to near 40% for each site.
Of course, the Don Rak cemetery contains the most remains of those that were collected after the war using the rosters and records that were the source of the COD information being discussed here. Remember, too, that by Apr-May 1944, just about all of the POWs had been consolidated to the camps in and around Kanchanaburi. No matter where they had worked or to which of the many work groups they were assigned, many men continued to die of the effects of their work; all would have been consigned to Don Rak. Thousands were eventually hospitalized and some died at the huge new hospital created in Apr 1944 in Nakorn Pathom, but only 55 deaths are registered as occurring there. Presumably, all of these post-construction deaths would have eventually been interred at Don Rak or possibly ChungKai. As opposed to the late (1945-47) burials at the other cemeteries, the 500 1945 burials at Don Rak make sense in that most of the POWs where consolidated into the KAN area camps and Nakorn Pathom hospital. Many of the recorded locations are ‘follow-on’ camps like Tha Maung and PrachuapKiriKan. Once again, H & F Forces muddle the data. A special hospital had to be created for them in Kanchanaburi. As such, 57% (350/612) of the deaths noted to have occurred in Kanchanaburi seem to have occurred at that facility.
 The 1946-47 burials at Thanbyuzayat are mostly of Indian troops who may likely have not been TBR POWs. Most of the 27 1946 burials at Don Rak are Dutch. These could very well have been TBR POWs who had not yet left Thailand due to the political situation in Indonesia (Dutch East Indies). So, too, the 1945 burials in Burma. But as to why they would have been re-buried there so late is not clear.