I used to think the same.
But I have experienced how most thai females including farmgirls/bargirls take a pride in teaching correct and polite thai to foreigners.
On more than one occasion in bars, I have recieved comments on my language and was told: That is not a polite way of saying it.

"But, but you use that expression yourself"?
"That is different, I am thai"

Well, fair enough.