There were literally dozens of work camps established along the length of the TBR; one list has 65 separate places named. In order to complete the project as quickly as possible, camps were placed every few kilometers and the workers assigned completed the railway in their sector. So work was going on more or less simultaneously all along the length of the rail line.
All the camps were generally the same in their basic construction. Some were quite small housing a few hundred for a few weeks to months before they were moved to a new section of the railway. Others were larger and semi-permanent.
The Petchburi POW camp has a unique place in this saga. Two USS Houston (CA-30) Survivors: James W. “Red” Huffman, Coxswain, USN and Lanson H. Harris, Aviation Machinist Mate 1st Class, USN escaped capture at that POW camp. In his excellent book Ship of Ghosts—the Story of USS Houston, FDR’s Legendary Lost Cruiser, and the Epic Saga of Her Survivors, author James D. Hornfischer details the entire July 1945 escape episode starting from page 374 (hardback version).
Also the story of the 4 US POWs who found themselves at the Ubon camp is detailed in Ray Withnall’s book. Their fortuitous arrival in Bangkok and flight to Calcutta is one of the more unique side-stories.