Cognomen Siwatchaya (Siwatchaya 
) , all over the world, is a very rare family name. The surname Siwatchaya is habitual in South-eastern Asia, particularly Thailand, where it is a very rare surname. More prevalently, Siwatchaya is the forename as well as the last name.
Kosol, Atchariyadecha, Trongtrakarn, Tipmontri, Pholpipattanaphong, Kunkhunthod, Naknakorn, Thongsri, Dusitanon, Chittayasodhara, Phoprasert, Osaithai, Tamanee, Punputh, Khianjoom, Soksamran, Morsuya, Mantham, Nuimai, Sirithai, and Khanuengkitkong