Thai people greet each other with a gesture similar to the one in the picture opposite. Thai people do not shake hands like people in the west. They place the palms and fingers of both their hands together as in a prayer position in the center of their bodies and at different levels depending upon the level of gesture as explained below.
This thai greeting gesture is called a "wai" , it is pronounce more like "why" in English.
The greeting gesture is also accompanied with a slight bow. The various position and gesture can be very graceful and expressive, show different degrees of respect, authority, submissiveness happiness and obedience. The Different levels of position of the joined hands show different degrees of respect. The higher the joined hands are held in relation to the face is an indication or more respect. The wai is also used to say "sorry" or "Thank you"
For Thai people the gestures are complex but foreigners are not expected to understand this aspect of Thai culture in detail. But for those who do try to understand and participate correctly the you start to be more integrated into Thai society and culture.