Cognomen 凯 (凯 
, Khai 
, Cay 
) , all over the world, is a widespread surname. The last name 凯 is characteristic of Malaysia, where it is quite a common surname, China, and Myanmar (explore the name in all countries). More frequently, 凯 is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| 凯, Kǎi | China |
| Khai | Mongolia, Myanmar, Malaysia, Vietnam, China |
| Cay | Myanmar, Malaysia, India, Vietnam, China |