All Travellers to Bangkok
Do not buy any jewellery from Bangkok, its a scam and locals and tourists are involed and make huge bucks by ripping off tourists by conning them to buy gems. They will tell you all sorts of stories and convince you that you can double your money by selling it in another country. Do not fall for this scam.
Gemstones are the Tourist Police's number one received complaint, don't even think about buying any unless you are a real expert. You will be ripped off, and you will regret it. A number of legitimate looking shops sell fake gems to stupid tourists day after day, although the authorities are trying to clamp down on it.