Marijuana is illegal in Thailand except for authorized medical use.
Locally produced marijuana extracts (with less than 0.2% THC or tetrahydrocannabinol, which is the main psychoactive compound in cannabis) are exempted. Extracts with these low levels of THC can be used in food products, herbal tea, etc. There are many "Ganja Cafe's sprouting up around Thailand which are growing in numbers. There's one that just opened up at Jomtien Beach - near the gay beach, and another one right next door to Immigration.