You don't really have much choice any more - only SQ or GA from SIN to DPS and return, with a couple of flights weekly on Qantas.
Selecting two random out and in dates in early May, the QF website gives a fare of SGD365 return, including taxes, and the same two dates on SQ give me SGD639 return incl taxes on the SQ www.
Without knowing your min/max stay or selected times, it may well be very different for that QF fare, but at least there is another option for you to play around with.
GA these days is a far different kettle of fish from the old "loathed" GA. Under manangement guidance and control from Lufthansa, they have turned things around for the most part - I wouldn't be so quick to dismiss them for just a two hour flight.
Failing that, the only other options I can think of off the top of my head are Malaysia over KUL, Cathay over HKG and Continental over GUM, or Qantas via Oz, Air NZ via AKL.
Cheers.