what its mean Windows 7 Pro OA SEA

can any one tell me what version is this Windows 7 Pro OA SEA what is a meaning of OA SEA ?

I believe it's a Microsoft Open Agreement license for vendors or sellers in Southeast Asia. It's a special volume licensing program for government organizations, health organizations, educational institution, qualifying nonprofit organizations, and multinational organizations.

Microsoft Volume Licensing - Microsoft Open Programs

Did you buy your computer through one of these organizations as a qualified buyer (while you were a student, for example?) If no, it's possible the licensing terms were not met.

my brother got laptop from his company ...

It means Offline Activation which is how preinstalled OEM is activated at factory. The SEA means it is Southeast Asian regional Language group.

You can however most likely use the licensed version from Step 1 here to Clean Reinstall - Factory OEM Windows 7.

thanks brother