The border between Kanchanaburi and Burma is as porous as it gets, easy to cross. Before I went to extensions of stay I used to do border hops at Phu Nam Ron in Kan. A minibus used to bus us across the border to Burmese Immigration. A couple of times on the way back into Thailand people were being trafficked into Thailand as the bus was stopped short of the border and they disappeared into the jungle with a guide. I reported this to the Police in Thailand. Their response? "Nothing we can do, the Army control this border".