Cognomen Riai (Riai 
) , worldwide, is a very rare surname. The surname Riai is habitual in Ireland, where it is a rare surname, Indonesia, where it is a very rare surname, and Malaysia, where it is an extremely rare surname. Not in comparison with a country's population, it is the most numerous in Indonesia, India, and Ireland. More frequently, Riai is the forename as well as the last name.