One thing you will find in Hong Kong is that rules are rarely enforced unless your actions cause problems with others to the point they report you and then the authorities are forced into action.
In other words, if you live alone, and politely and quietly bring someone into your flat, and this causes no disturbances with others I'm sure you will be fine. If your guest becomes loud or bothersome, that could be a problem. Just be cool, respectful and polite and no problems.