Which Bachelors degree should I opt to pursue MBA in HR?

You should opt for a management course in the UG. You will get lots of benefits of the same in Masters.

If you want to go for management, then you can go for BBA course. You can start preparing for CAT and take admission in MBA HR.

It is recommended that you do BBA degree before MBA HR. BBA program usually includes general business courses and advanced courses for specific functional areas such as finance, HR, IT, marketing etc. Thus you will get exposure to all management functions before you specilaise in HR at PG level.