The very best advice I can give after more than 20 years in Thailand is to avoid all kind of illegal drugs, but in the case some people cannot leave without weed they can go to a doctor with a cannabis license and get a THC oil prescription than register to Narcotic Control Board so they can carry and cure themselves safely all around Thailand but even you get a prescription that will save you from being caught with illegal cannabis it is always better to keep a low profile, never forget that you are a guest here.