Formal:
* കുട്ടി (kutty) - This is the most common and neutral term for a young child, regardless of gender.
* ബാലൻ (baalan) - This is a more formal term for "boy".
Informal:
* പയ്യൻ (payyan) - This is a more informal term for "boy".
* കുട്ടൻ (kuttan) - This is another informal term, similar to "kutty".
Note: The specific word you choose will depend on the context and your relationship with the boy. It's always best to err on the side of formality, especially when speaking to someone you don't know well.