There seems to be a lot of mis-information circulating, particularly on various FACEBOOK and YOUTUBE sites, that the existing bridge at Kanchanaburi (actually ThaMakam) is not ‘the real one’. People claim that it is a replica, constructed as a tourist trap. I can assure you that IT IS REAL!
Although the US POWs had nothing to do with its construction (with apologies to William Holden), British and Dutch POWs constructed first the wood/bamboo bridge then the iron/concrete bridge a few hundred meters upstream. The iron portion of that bridge as it sits today was looted from Java and shipped to Kanchanaburi. The two center spans were reconstructed post-war to replace those destroyed in the June 1945 bombing. The Thais intentionally replaced them with rectangular sections to differentiate them from the original semi-circular sections.
It must also be said that the Japanese were excellent railway engineers. Unlike the movie, they needed no help from the British in planning any portion of the railway. British LtCol Toosey (not Nicholson of the movie) was actually an artilleryman, not an engineer! [see Section 3.7.2]
We know precisely where the wooden bridge was due the existence of the Thai-anusorn Shrine as shown in this aerial recon photo:
There are even some who confuse the WangPo trestle [Section 8.6] with ‘the Bridge over the River Kwai’. How that is possible I do not know. Another point of confusion that pops up with some frequency are references to the war cemeteries as ‘UN cemeteries’ This happens most frequently on GOOGLE EARTH and never seems to be corrected. Chalk it up to a lack of education and a failure to learn any true history!
The Commonwealth War Graves Commission (based in London; CWGC) tells its version of the story:
https://www.cwgc.org/our-work/blog/the-true-story-of-the-bridge-over-the-river-kwai/