Gambling Laws in Thailand\n\n (Source) Land-based Casinos are banned in Thailand under the Gambling Act 1935. Other than betting on a horse race and government-sponsored lottery, if anyone is seen indulging in gambling activities, then they can be imprisoned for one year or asked to pay 1000 Baht as a fine.
Source Any form of gambling is illegal in the cities of Thailand, which includes Bangkok. Horse racing and official State Lottery are the only two types of gambling allowed in Thailand; any other form of gambling is strictly illegal. But despite these strict Thai Laws, underground casinos are widespread in Bangkok.