Like most places, Thailand’s business dress code is conservative. Dark (but lightweight) suits and ties for men, and knee-length skirts or suits for women, who should also keep their shoulders covered. Observe business partners to determine when you can go more casual.
The traditional Thai greeting is the wai: palms together in a prayer-like position just below the chin and your head slightly bowed. Thais don’t expect foreigners to initiate a wai, but it would be rude not to return one. Address everyone by Khun, followed by first name.
Heading to meetings, leave plenty of time for traffic, especially in Bangkok. Initial meetings are for getting to know one another; getting down to business right away may not be received well. Thais laugh easily and a foreigner can cover errors and social mistakes by laughing.
Offer and receive business cards with the right hand. Make sure you have an ample supply of bilingual (English and Thai) business cards. If you are doing business across Southeast Asia, make sure you keep your cards sorted by country; it is not only embarrassing but also insulting to give someone a card in the wrong language.
Don’t say anything negative about the royal family; you will not only ruin the occasion but may face legal consequences. Be respectful of images and statues of Buddha. Never touch a monk. Do not touch anyone’s head. Don’t pass things with your left hand or point with only one finger.