Old steam engine from the death railway.
The WWII and JEATH War Museum has to be the most 'unusual' of Kanchanaburi's death railway museums. The truly eclectic collection covers not only the war, but also the history of the area, and there's even a room dedicated to all the ladies who have held the title of Miss Thailand.
Rail boxcars were used to transport POWs to work on the railway, then used as cells for prisoners that misbehaved.
The privately owned museum seems to be in a constant state of renovation, yet the displays are rather poorly maintained, and there's very little order to the exhibits. The English translations of signs and labels are among the worst you will see in Thailand.
I found the museum very interesting, but more for the sheer audacity of the collection than for any new perspective they provided.
The World War II & JEATH War Museum is located on the river near the rail bridge. Admission is 40 Baht (1.04 USD).