Cognomen สิธยา (สิธยา 
, Sittaya 
) , throughout the world, is an extremely rare last name. The surname สิธยา is habitual in Southern Asia, particularly India, where it is an extremely rare surname. More frequently, สิธยา is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| สิธยา | Thailand |
| Sittaya | Thailand, India, United States |