Cognomen Siwathao (Siwathao 
) , all over the world, is a very rare last name. The cognomen Siwathao is habitual in South-eastern Asia, particularly Thailand, where it is a very rare surname.
| VARIANT | COUNTRY |
|---|---|
| Siwathao | Thailand |
Phitsauaong, Saowanee, Lakkhana, and Phonchanok