Airlines have these agreements to help with selling unusual tickets and especially rerouting in case of IRROPS.

It does NOT mean there is any kind of obligation to through check luggage when the customer decides to be creative with ticketing.

You would need to be very lucky and find a friendly checkin agent at BKK for this to work.

Without a visa for India you also have a very real risk of being denied checkin at BKK in the first place.