The Hands

Ideally, you should do as little as possible with your hands. Leave them hanging by your side. You should never use them to slap someone on the back or messing with someones hair. In fact, be careful about touching people anywhere and never touch across the sex line. The safe exception is a polite touch at the elbow, usually to draw attention but sometimes just for the sake of it, between friends and colleagues.

Pointing

Pointing with a finger is less offensive than pointing with a foot and is acceptable for objects (except sacred objects) but not for people. If you really need to point someone out, try to indicate who it is with a slight upward movement of the chin. Thais are so sensitive about being pointed at that even the girls in the massage parlours wear numbers so that you don't have to point out which one you want.

Don't wave your hands

In some cultures, the hands are used to underline what you want to get across. This will only make you less understood because Thai people will think you are angry and you will not get any respect since you obviosly can't keep a cool heart.

Getting attention

To get attention you are better off to use a quiet voice than your hands. Never clap or snap your fingers and never hiss. The correct way to call attention with your hand (if absolutely nessesary) is to keep your hand with the palm facing down and move the fingers rapidly towards you.

Throwing

It's considered quite slobbish to throw things, even if it's only a box of matches. If it's a semi sacred object (food for instance) than it's rude. If you throw a sacred object, like a Buddha image for instance, then you're asking for trouble.

Pockets

After reading this you might come to the conclusion that the best thing to do is to keep your hands in your pockets. Wrong. This is considered very bad manners. If you really need to do something with your hands, why not pick your nose. If not the best of things to do, at least it's not considered taboo as in the west.