Where is one in BKK?

Can not help , this is far to Hi-Tech.

They normally use the legions from Isaan to handwash cars.

Go for expensive places ,like Hi-end Department Stores , to ensure a better handling as at the pump stations .

When I go shopping at Emporium, I leave my car (not every time) at the car wash of the parking garage. They park it, wash it and have it waiting when I come out from the movie or shopping. 140THB for exterior only (with a bit of front seat interior cleaning too). I think it is 200THB if they do interior vacuuming too.

I have been to one drive thru car wash at a gas station on Satorn going toward Rama IV.

When I go shopping at Emporium, I leave my car (not every time) at the car wash of the parking garage. They park it, wash it and have it waiting when I come out from the movie or shopping. 140THB for exterior only (with a bit of front seat interior cleaning too). I think it is 200THB if they do interior vacuuming too.

I have been to one drive thru car wash at a gas station on Satorn going toward Rama IV.

Yes theres one on Sathorn....its at the Shell garage next the the Australian Embassy.......don't use automatic ones myself......they scratch the paintwork and handwash is normally cheaper