The Art Of Affection
Don't touch, hug or kiss Thais when you meet them. Thai people are not familiar with this kind of body language. It may be, as some have observed, that we Asians are shy. In general, any physical contact (apart, these days, from a handshake) is considered inappropriate.
Although you may do it out of respect and with all good intentions, it will make them feel uncomfortable, especially if it is done in public.
Most Thais are not used to this type of gesture and have no idea how to react to it. It may leave everyone, including you, feeling awkward.