The symbolism of the graphic is clear - Kanchanaburi is a popular province for tourists and all of the items found in the graphic are well-known attractions in the province.Most prominently is the railway bridge of the River Kwae (The Bridge on the River Kwai) to the left. Below the bridge is one of the river restaurants, which are found a lot in Kanchanaburi town. To the right are the Three Pagodas found at the boundary to Myanmar at the Three Pagodas Pass. The waterfall below is the Sai Yok waterfall. The setting sun in the middle refers to the location of the province in the west of Thailand - the Thai word for "west" translates as "where the sun sets".
The design announced in 2006 [Gazette] also shows the bridge and the pagodas, and I assume the somewhat strange looking water at the left border is again the Sai Yok waterfall.