Here you can see Japan's set up to fight (or not) in southeast Asia.
The Siamese militia force is set up in the hinterlands. If the Allies cross the mountains to bypass it, it will rail down to Bangkok to hold the city (for however long such a weak unit can do so).
The Japanese expedition to Burma has been deemed a success, for as long as it lasted, and it is no longer a defensible position, given the shortage of land units to form and hold a line, and the shortage of convoys to keep a supply line open.
As such, the Burma force is now poised to cross back over into Siam, to be shipped by sea to defend other overseas objectives...

















