Surname ฤทธิ์ศักดิ์ (ฤทธิ์ศักดิ์ 
, Rittisak 
, Ritsak ) , in the entire world, is a rare cognomen. The family name ฤทธิ์ศักดิ์ is habitual in South-eastern Asia, particularly Thailand, where it is a rare surname. Also, ฤทธิ์ศักดิ์ is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Ritsak, ฤทธิ์ศักดิ์ | Thailand |
| Rittisak | United States, Thailand |