India does require a visa, but there is a CX flight BKK-BOM, then connect to CX either in BOM again back to HKG on the one flight number via BKK, or leave from DEL and make your own way between the two. You could get the Indian visa from the enbassy in BKK, of you have time. If you don't have any time for visas, then the best flight to take would be to NRT, you could fly with JL from next week, and them back down to HKG with CX.