Hi
Have given GMAT last year and got 630. Due to my work schedule, I think i would be unable to re-write. However, I have 6 years of work-exp now. 4 years in Big 4 in Mergers and Acquisition advisory, 1 year in Real Estate Private Equity in India. Low on extra-curricular activities. Decent grades in undergrads. Primary qualification is Masters - Chartered Accountant.
I intend to do MBA primarily for international networking and jump a few ladders in my career progress. Please suggest whether I should applyw with this score or should re-write again. I want to apply to tier 1 schools only like HKUST, Insead or probably Wharton.

You would not be a competitive candidate at any top school with a 630 GMAT unless you had exceptional undergraduate, professional or extra-curricular success. From your profile, you don't sound like your application would stand out very much. At the schools you mention, would would need to closer to or above 700.

Some other schools I would suggest to you:
SP Jain Center of Management
Babson College: Olin
Manchester Business School
Vlerick Leuven Gent Management School
SMU: Cox
University of Georgia: Terry
Texas A & M University: Mays
Lancaster University Management School
SDA Bocconi