Unlike in the US, UK, etc., employment contracts in HK can be written to favor employers. If you just can't stand to stay there another day, your employer cannot actually force you to show up at the office and work, but they can (if they for some reason pursue the issue) take you to court for damages and get an injunction to prevent you from working for another employer (in Hong Kong) for the notice period. If you have a particularly bad relationship with your employer, they can report you to immigration (tell them that you are in violation of your contract) which will make it harder to get a new employment visa.
Best bet is to just talk to your employer and see if they will shorten the notice period. And, get their reply in writing. Good luck.