Cognomen Onsaeng (Onsaeng 
) , in the world, is a very rare last name. The cognomen Onsaeng is habitual in Thailand, where it is a very rare surname, the United States, where it is an extremely rare surname, and China. Very seldom, Onsaeng is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Onsaeng | China, United States, Thailand |