Family name ถนอมสิทธิ์ (ถนอมสิทธิ์ 
, Tanomsit , Thanomsit ) , across the world, is a very rare surname. The family name ถนอมสิทธิ์ is habitual in South-eastern Asia, particularly Thailand, where it is a rare surname. Much less frequently, ถนอมสิทธิ์ is the forename as well as the last name.