Be Seen Not Heard
One of the most evident things you will notice on any trip to Thailand is exactly how different their customs are to our own. The Thai way of life is very much based on the Buddhist religion and this is blatantly evident almost as soon as you arrive.
While Thais have mostly come to expect foreigners to turn up wearing shorts and short tops, you will gain much more respect from the locals if you dress modestly. This is especially true for the women who should also remember never to touch monks. Temples are one place where you must dress appropriately and be respectful. You are free, indeed encouraged to look around the temples, but you should be quiet and dressed.
Respect for the king is also something that is looked on as being very important. Twice a day, the national anthem is played in public places and you must be stood when this is playing. You can, and probably will, be arrested if you do not stand. This respect has been earned because the current King is one who has done a lot for the Thai people.