I think you'll find blr-BKK-hkg Economy passenger will have a 20kg plus 10kg bonus allowance. All Thai international flights are 20kg base. Only 20kg allowance for domestic as well.

Thai will happily tag bags to SFO, just checkin online with Cathay, and bring your e ticket to India Checkin. From memory its 4 or 5 city max for bag tags. I once tried 6 and it confused the airline and caused a mini meltdown at Turkish airlines checkin !

http://www.thaiairways.com/en/plan_m...ormation.page?