我想申報成為NON-TAX CITIZEN (canada), what can I do ?

This can be done DIY or by hiring a professional accountant to do that for you. You can visit the website of Revenue Canada to request for a brochure, this explains things that you will need to do to sever your ties with Canada. You can also fill out an application form to apply as a non-resident for tax purposes.

Remember to clearly cuts out all ties with Canada, e.g. cutting up your Canadian credit cards, abandoning your previous usual place of abode in Canada etc are gestures that might be required to convince Revenue Canada that you are genuinely leaving Canada for good. If you still maintain your child or spouse in Canada while working in Hong Kong yourself, you probably do not qualify to claim as a non-resident for tax purposes.