Surname ฤทธิ์สิทธิ์ (ฤทธิ์สิทธิ์ 
) , in the world, is a very rare last name. The cognomen ฤทธิ์สิทธิ์ is characteristic of South-eastern Asia, particularly Thailand, where it is a very rare surname. Much less frequently, ฤทธิ์สิทธิ์ is the forename as well as the last name.