Technically, Thai law does not specifically mention online gambling as prohibited, however, law enforcement officials view online gambling as falling under conventional gambling. Thus, local police will still arrest anyone who takes part in online gambling whether they are an operator, a bookie, or a player.
You just have to stick to legal, regulated online casino sites such as BetMGM, Caesars Palace Online Casino, FanDuel, Betway, bet365 and BetRivers. They offer great casino game ranges and they will pay out quickly and without any issues if you win.