I have 5 year sales executive experience salary rs 20000/mon resign my job and doing mba fulltime is worthone?

Depends on your career goals. When you complete the MBA you may wind up in a job at less than your current income. But you could also wind up in something much better for you. Find out what graduates are earning from the school you plan to attend. Such information is available. Consult the Official MBA Guide. It's a comprehensive free public service with more than 2,000 MBA programs listed worldwide. It allows you to search for programs by location (US, Europe, Far East, etc.), by concentration (finance, marketing, aviation management, health management, accounting, etc.), by type of program (full-time, distance learning, part-time, etc), and by listing your own criteria and preferences to get a list of universities that satisfy your needs. Schools report their accreditation status, tuition cost, number of students, class sizes, program length, and a lot of other data. Schools provide data on entrance requirements, program costs, program characteristics, and much more. You can use the Guide to contact schools of your choice, examine their data, visit their web site, and send them pre applications. You can see lists of top 40 schools ranked by starting salaries of graduates, GMAT scores, and other criteria. It's the best service available at http://officialmbaguide.org. A large number of MBA graduates are starting their own businesses, sometimes together with classmates. Review your plans and decide what you want to do. Any advice you get here is only a starting point. No one here knows your situation well enough to give you meaningful advice.

Depends on what you want to do with the MBA. To be honest with you, if your $20K/month job is secure, odds are that getting your MBA won't improve your job prospects if you want to stay in the sales executive field.