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.
One or two anecdotal instances don't mean a pattern, but the 2-3 times I checked BOM-BKK fares over the past year, Indigo were more expensive than Jet. Only Cathay were cheaper.