Cognomen Piboonsak (พิบูลย์ศักดิ์ 
, Piboonsak 
) , globally, is a very rare last name. The last name Piboonsak is characteristic of Thailand, where it is a very rare surname, and China, where it is an extremely rare surname. More frequently, Piboonsak is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| พิบูลย์ศักดิ์ | Thailand |
| Piboonsak | Thailand, China |