encountered one such driver once during my 1st time in bangkok few years back.
Asked if he is gonna have the meter on, and got in after he nodded, but after the doors closed he yabbled on saying his meter is spoilt, cant on, and quoted me 200 for a trip from asoke to petburi soi1 !
told him "up to u, meter no on, me no pay" and after a few tries "explaining" to me why the meter was spoilt, the meter miraculously recovered!!
however i gave him a round change (fare was 72+ thb, i gave him 90) upon arrival, afterall, his trick didnt work but while in thailand, give them some face and both goes off happy.
my say is, when the thai drivers pulls a stunt on you, while you have to be firm on ur stand however, but do not bring out any aggression... afterall you're in a foreign land and thais rather have thier face saved den to have any sorta confrontation. "A cornered kitten kills"