Surname ธรรมไทย (ธรรมไทย 
, Thamthai , Thammathai 
) , around the globe, is a rare cognomen. The cognomen ธรรมไทย is habitual in Thailand, where it is a rare surname, and the United States, where it is an extremely rare surname.
| VARIANT | COUNTRY |
|---|---|
| ธรรมไทย, Thamthai | Thailand |
| Thammathai | United States, Thailand |