OK, now that we've scared you....
It can be done..... but not quickly or directly. Basically the NE Monsoon will be at it's peak in January, so a direct Singapore to HK run isn't advisable. I could even stretch that to it's bloody stupid.
But the Monsoon comes in surges - So one way is to break down the journey into small bits and pick your weather
windows as they come and maybe push on if they let you. Perhaps go along the lines of Singapore, KK, Palawan, Busuanga, Mindoro, Luzon (all the way to Bolinao), Hong Kong
. keep them all to starboard.
I've done this trip twice at that time of the year (well feb/mar) and once it was fine and once it was hell.
Personally, I'd be in no rush to do the Luzon to HK bit before March.