The Thai greeting referred to as the wai (Thai: ไหว้, pronounced [wâːj]) consists of a slight bow, with the palms pressed together in a prayer-like fashion.
It has its origin in the Indic Añjali Mudrā, like the Indian namasté and the Cambodian sampeah.
The higher the hands are held in relation to the face and the lower the bow, the more respect or reverence the giver of the wai is showing.
The wai is traditionally observed upon entering formally a house. After the visit is over, the visitor asks for permission to leave and repeats the salutation made upon entering.
The wai is also common as a way to express gratitude or to apologise.