Family name เพชรชัย (เพชรชัย 
, Phetchai , Petchai 
) , throughout the world, is a rare cognomen. The cognomen เพชรชัย is characteristic of South-eastern Asia, particularly Thailand, where it is quite a rare surname, and Malaysia, where it is an extremely rare surname. Much less frequently, เพชรชัย is the forename as well as the last name.