I am learning the Taxation. According the taxation law, you have to report your global income to CRA even if you have left Canada if you are still maintencing the ties with Canada. The primary ties are:
1) Dwelling
2) Spouse or Common-law partner
3) Dependents
The secondary ties are many types such as driver license, passport, health cards.
In one word, it is a very complex problem. It is better for you to get advice from professional accountant.