It's used as a polite question, similar to "May I...?" or "Is it possible to...?" in English.
Here are some examples of how it might be used:
* "Ke yi ma?" (Can I?) - Used when asking permission to do something.
* "Ni ke yi bang wo ma?" (Can you help me?) - Asking someone for help.
* "Wo ke yi chi ma?" (May I eat?) - Asking permission to eat something.
It's important to note that the tone and context of the situation can influence the meaning of "Ke yi ma".