Don't point the soles of your feet/shoes at people is the other big one apart from the head touching.

In business the etiquette is reasonably "worldwide standard" unless you are dealing with a very senior/old figure. If the people you are dealing with are younger than you then they may wait for you to offer a handshake, but then they would take it. If they regard you as eminent/senior then they may also use the "wai" (the hands together and bow). Opinions differ on how to respond to this. My preference is normally to make a slight bow of the head in acknowledgment, but some westerners return the wai. The most important thing in my mind is to acknowledge it somehow, but don't try to be too "Thai" - they know you're not and they expect you to behave like a (respectful) foreigner, not like a Thai.

If you Google "wai" you can get much more advice on this...