Bitcoin in Thailand is not banned, it just needed to be regulated by the local SEC. Only a few exchanges are allowed to fully operate in Thailand. As now, the most common exchange is
bitkub. I was used to play with coins.co.th but it hasn't been updated since years. Bitkub is a good growing exchange which is following the steps of Binance. They are "copying" Binance basically. That's good for Thai people who wants to invest in crypto and diversify their portfolios with some more options.