Family name เที่ยงตรง (Thudchai 
, Thiangtrong , เที่ยงตรง) , globally, is a rare surname. The cognomen เที่ยงตรง is characteristic of South-eastern Asia, particularly Thailand, where it is a rare surname. Much less frequently, เที่ยงตรง is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Thudchai, Thitthong, Thiangtrong | Thailand |
Thiabthathong, Thiangdah, Thiangdirit, Thiangngok, Thiangthin, Thiangthrong, Thiantrong, Thiapthathong, Thiengtrong, Thittthong, Thudthieng, Thuengdee, Tiangtholkrang, and Tiengtit