Cognomen ทองธัญรัตน์ (ทองธัญรัตน์ 
, Thongtunyarat , Tongthanyarat ) , across the world, is a very rare family name. The surname ทองธัญรัตน์ is habitual in South-eastern Asia, particularly Thailand, where it is a very rare surname.
| VARIANT | COUNTRY |
|---|---|
| Thongtunyarat, ทองธัญรัตน์, Tongthunyarat, Tongthanyarat | Thailand |