The most common pose for Buddha images in Thailand is the seated image displaying the Bhumisparsha Mudra gesture, more commonly known as the "subduing Mara" pose.
Mara is a demon who attempted to lure the meditating Buddha away from the path of enlightenment. The story goes that the Buddha was meditating on his way to attaining enlightenment when Mara came to try and force or tempt him from the spiritual path - this was, in effect, Mara's "job".