Jumping ship is highly frowned upon by the Immigration Office. Your work visa is valid only with the sponsor who employed you and that visa is valid as long as your contract is. If you terminate your contract, you are only entitled to remain in Hong Kong for two weeks thereafter. Your visa is non-transferable, so a new employer will have to sponsor you and apply for a new visa for you to work. All the usual visa requirements must be met, including evidence that the employer was not able to fill the post locally. If you happen to be highly qualified and specifically skilled, you can be headhunted for other jobs or find openings on your own.