Application for registration of trade marks needs to be made to each country or jurisdiction separately.
Each place will independently decide whether it will register a trade mark in that place.
So, protection for a trade mark registered in Hong Kong does not extend to the Mainland China nor elsewhere in the world. Similarly, a trade mark registered in the Mainland China or elsewhere in the world does not cover Hong Kong.
You can apply for the registration of a trade mark in each separate country or jurisdiction where you want to seek protection.