The Buddhist monks and the King are to be treated with the utmost respect. This respect is carried over the statues of the Buddha and photographs of the Royal family, especially H.M King Bhumibol. Treat such objects with disrespect and you could easily find yourself in a gaol. Do not enter any temple, whether Buddhist, Muslim or Hindu, in shorts and without first removing your shoes or sandals. Do not point your feet at anyone in front of you, or at statues of the Buddha.
Westerners have to be particularly careful when they sit on the floor and lean back against a wall.
Do not pat or playfully pull the hair of a Thai child, let alone an adult. It is considered grossly offensive. The top of the head is considered to be the most spiritual part of the body. No woman, or group of women, should approach a monk unless he is, or you are, accompanied by a male 'chaperone'. A monk may not talk in private with a woman without a chaperone.