Cultural Tips for Thailand

Thais are very easy going and would rarely tell you if you are doing something that offends them. However, here are few things to think about before you arrive:
Heads: Never touch an adult on the head. Thais consider the head to be the highest part of the body (spiritually) and would feel incredibly uncomfortable if you were to do so. Children under the age of 10 can be touched on the head in a playful manner, but the best rule of thumb is just to not do so.
Feet: On the opposite side of things, Thais consider the feet to be the lowest part of the body (spiritually) Therefore, it is extremely rude to do almost anything but walk with them. Do not put them up on chairs, ledges, etc to relax. Do not gain someone’s attention by tapping him or her with your foot. Do not open or hold open doors with your foot. This might seem a bit extreme and strange, but it will quickly become second nature.
Noses: Try not to blow your nose while eating. If you need to refresh your nostrils, it is best to get up and step away from the table.
Shirts: In busy centers, keep your shirt on (unless on the beach of course). Trust us, despite the Thais not sweating as much as foreigners, everyone is hot. Imagine if everyone walked around with their shirts off – Someone Call the Fashion Police!!
Naughty Bits: Do not tan nude at any time in Thailand. Thais consider it very inappropriate and rude to expose your private bits and pieces in public. It doesn’t matter if you see others on the beach doing it – the Thais don’t like it; as mentioned before they are just too polite to tell you.
Royalty: Refrain from speaking publicly about the Royal Family of Thailand. Thais highly revere all members of the Royal Family, to the point that it is almost rude to speak publicly about them out of respect. Never speak about any past or present Royal Family members passing away either.
Monks: Women must never come into physical contact with or directly hand anything to a monk.
source http://www.smilingalbino.com