Theres a caravan dealer on facebook, theres a guy in CM who sells pickup bed backs like Americans often utilize.. There were some cheap buses sold off recently which would have made superb traveler / hippy busses, if I had more time space I considered one as a plaything.
All that said, Thailands climate is not great for them, the infrastructure isnt readily there so it needs to be a wild traveler type setup, and rooms can be found so cheaply that they dont have the same comparative upsides as expensive hotel countries.
I like this style of travel, I have done multiple N Africa overlanders, brother had a converted merc 7.5 tonner as a Portugal / Morocco surf hunter for years.. I grey up on and off the road lifestyle as a child in a bunch of things from converted horse transport, military a postal van, a 4x4 one for Sahara, etc. Even enjoying them I wouldnt be too serious about one in asia.
I actually know of a nicely restored one for sale in CM at a fair value..