JAL's rate for Jan is $705 i think all in, per pax.
looks good ?
Yup, compared to $680 from TransAsia Airlines, I'd take JAL $705 anytime
You get to fly in the new 787 to Tokyo ya

And you can choose to fly to other Hokkaido airports after that if you want. There's no need to restrict yourself to New Chitose only.
Do check out ANA as well. Both are equally convinent. The trick is to find a flight that lands in the SAME airport as your connecting flight to Hokkaido. This is very impt. There is no need to waste over 1 hr on the shuttle bus just hoping you'd you reach the other airport in time for your connecting flight.
Look through ANA and JAL flight time table. They DO have flights from SIN to either Henada or Narita. And from there pick the corresponding connecting flight to Hokkaido from the same said airport. It CAN be done.
I was quite amazed when I downloaded ANA and JAL timetable. There's really no need to chiong from Narita to Haneda (and vice versa) if you plan your trip carefully. Some flights to Hokkaido may be operated by JAL Express using small 737... but who cares, it's only a 1.5 hr flight and even an antique 727 can bring me to my prefered Hokkaido airport safely and on time