On the contrary.
I have been asked for or invited by about 15-year-olds to "smoke weed". And I have witnessed such activities from a distance. Out of tourist areas, "smoke weed", "fuck you" and "good morning teacher" are the phrases I hear most often when I walk past Thai youth. "Fuck you" is not personal, it's just the only English they but don't understand, and are happy to show off their knowledge of English. This is proven by "good morning teacher" being used at any time of the day or night.
"Smoke weed" is widely accepted and practiced among lo-so Thais. But still, I can't advice the op about quality and prices.