Family name ใด (Dai 
, ใด 
) , in the entire world, is a prevalent surname. The surname ใด is habitual in Cayman Islands, where it is a common surname, Bermuda, where it is quite a common surname, and China (explore the name in all countries). Measured by absolute frequency, it is the most numerous in China, India, and Indonesia. Very seldom, ใด is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Dai | China, Indonesia, Vietnam, United States, India |
| ใด | Thailand |