Cognomen เพ็ญชัย (เพ็ญชัย 
, Phenchai , Phengchai 
) , all over the world, is a rare last name. The cognomen เพ็ญชัย is habitual in South-eastern Asia, particularly Thailand, where it is a rare surname. Likewise, เพ็ญชัย is the forename as well as the last name.