this was announced about 4 weeks+ back yes, but full loads were perhaps because they are not dictating price on this route and undercutting to get loads. so maybe it was not lucrative enough. also, do remember that from BOM and DEL, you pay some of the highest airport charges, each of which are payable per flight, so they'd rather use their slots for something else, I guess. Customers don't see this esp. when they want to fly to BKK, they want ultra low fares.
From what I know, they were charging about INR 12-13k for BKK - BOM returns booked about 45 days in advance..next lowest was between INR 20k ( AI/ 9W) - 30K.. If it was not lucrative, they could easily have increased the prices to about INR 15k - 16k and would still be >20% cheaper than others and which is enough for many pax in this region..