Surname เก่า (Kao 
, Olden 
, Old ) , in the entire world, is a common last name. The surname เก่า is characteristic of Taiwan, where it is quite a common surname, Lesotho, and Cayman Islands (explore the name in all countries). Not in comparison with a country's population, it is commonest in Taiwan, the United States, and China. Very seldom, เก่า is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Kao, Old | Taiwan, United Kingdom, United States, Malaysia, China |
| Olden | United Kingdom, United States, Democratic Republic of the Congo, Malaysia, China |