Lately the tourist numbers dropped 20% in Thailand.
And the police is more active in Bangkok scaring tourists.
Tourists in Thailand Are Being Targeted by Corrupt Police
Friend of mine arrived by bus and they where checking all his bagage, so don't take it with you.
In Thailand i know 1 Island where there are even a sort of 'cofeeshops".
Further is best to let a bar girl get it and buy it, not buy on the street yourself.
I heard you can get it everywhere in Thailand, but i didn't bother to look for it.
More and more people go to Cambodia to smoke, no problem there.