Cognomen Wannajak (Wannajak 
) , all around the world, is a rare last name. The last name Wannajak is characteristic of South-eastern Asia, particularly Thailand, where it is a rare surname. Much less frequently, Wannajak is the forename as well as the last name.
Suwat, Nutthaporn, Thanyalak, Thanasart, Ploypailin, Yuttapon, Weerasak, Nutthporn, Nattakun, Terdkiat, Kanokwan, Kanitnicha, Supitcha, Monthana, Mahatsajan, Manthana, Patipan, Achita, Patcharapan, and Patcharaphan