You dont have to fill another basic registration. The last year basic registration will be valid. If the basic registration application has been accepted last time you can use it for the next time also. You can use that basic registration as long as you appear for PG exams. The only thing that you need to do will be when final registration dates are announced, you have to generate the RUC code, make the final payment and submit the final registration application using the same basic registration details.