Hi Alok322,
For many Testing Centers, a valid passport is enough identification. However, in a foreign country, there might be some additional requirements. If you know the location of the Testing Center that you'll be taking your Official GMAT, then you should contact the Center and confirm what the requirements are. If you are unable to find an email address or phone number for that Center, then you could visit the Center personally and ask your questions.
GMAT assassins aren't born, they're made,
Rich