Can you please confirm that you booked through Italian website for route DPS-BKK-BLR?

So the fare would have been sold in IDR currency and not EUR? And you say there were limited fare selections available?

The range of fares originating in one market may not exist in another. For example, fares departing Australia typically offer more fare varieties than fares from New Zealand. That sucks, but that is what THAI has decided to sell. It is possible that fares ex-Indonesia to India have some limitations.