Lao people traditionally greet each other by pressing their palms together to “Nop”, although it is acceptable for men to shake hands. The Lao address each other by the first name, prefaced by the equivalent of Mr. or Mrs., or if well acquainted, Mr. Uncle or Mrs. Aunt, or a courtesy title.

The Nop , the most common form of greeting in Laos, involves placing ones hands together in a prayer position at the chest level, but not touching the body. The higher the hands, the greater the sign of respect, although they should never be held of the level of the nose. This is accompanied by a slight bow to show respect for persons of higher status or age. The nop is not only an expression of greeting, but also an expression of thanks, of regret or of saying good-bye. It is appropriate for Laotians to shake hands with Westerners.

Source: http://factsanddetails.com/southeast-asia/Laos/sub5_3b/entry-2952.html