Surname Koai (Kai 
, Koai 
) , across the world, is a common family name. The surname Koai is characteristic of Malaysia, where it is a common surname, Macao, where it is quite a common surname, and Lebanon (explore the name in all countries). In absolute terms, this name is the most popular in Malaysia, China, and Myanmar. Likewise, Koai is the forename as well as the last name.