The actual building of the TBR was almost purely manual labor. The two exceptions were the use of elephants to move logs in the jungle and the occasional availability of air hammers in the cuttings.
There is a (possibly apocryphal) story of a camp guard handing over a camera to the Australian Team searching for POW remains. That is possibly the source of some of the above photos. Otherwise, they would have to be re-enactments of POWs working.
Here, too, the POWs made drawings of their efforts:
Most of the above photos were extracted from the on-line archives of the Australian War Museum:
The following set of photos seems rather odd in that they depict IJA soldiers (engineers?) working alongside Allied POWs. They have been posted to a Thai language site on FACEBOOK but without attribution as to exact place or time. IMHO, these appear to be AWM photos but this has yet to be verified. The general state of health of the Allied soldiers and their clothing suggests to me that these are post-war staged photos, but the reasoning is unknown.
The last photo above is labelled as: สะพานข้ามแม่น้ำ ข้ามห้วยและหุบเหวใหญ่น้อย or Kaam Huay Lae Hup Heaw Yai Nioi (?) If anyone can assist in putting a time or place to these or verify that they are from the AWM archives, please leave a COMMENT.