Hello,
If you are a current student outside Canada with an expiring study permit and you are not planning on returning to Canada at this time, you need to make a new study permit application. You can only renew a study permit application inside Canada, therefore that is why you will be initiating a new study permit application. It is highly recommended you get your application reviewed by an International Student Advisor to avoid rejection.
The application form you must be filling out for a study permit application is IMM 1294 not IMM 5257.
In the eligibility questions you will be asked:
Current location: enter the country you are currently residing outside Canada.
Do you have a valid work permit or study permit, and need a visa to return to Canada. You need to select "No" or else you will get the wrong application form (IMM 5257) which is for a temporary resident visa.
You should also include an explanation letter, explaining your circumstances regarding leaving the country.
Please do not submit an outside Canada new study permit application without talking to an International Student Advisor.