So I sent an email to the Canadian Embassy and this is what they said:
Good day,
Thank you for contacting the High Commission of Canda.
You can arrange an appointment to visit the Consular Section in Singapore to sign a Statutory Declaration in front of an officer declaring your common-law status, if you live in Singapore.
Please see below for notary instructions:
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Please forward us:
1) an affidavit declaring your common-law status;
2) documentary evidence (eg. tax return, bills, bank account, etc.) supporting cohabitation relationship between you and the other party for at least one year; and
3) copy your passport(s) via email. We will then book an appointment to witness your signature on the affidavit at the High Commission of Canada in Singapore when the signing officer is satisfied with the affidavit content.
Definition of common-law relationship in Canada:
http://www.servicecanada.gc.ca/eng/isp/ ... ecom.shtml
See attachment for a sample affidavit (please note that the affidavit is a free format and the applicant may amend the content as s/he sees fit).
Note: witnessing signature by the Consular Section does not guarantee the acceptability of your affidavit by the requesting authority. Therefore, you may wish to confirm the affidavit acceptability with the requesting authority in advance.
Fee: payable by cash or credit card (visa or master card only)
Witness of signature: CAD 50 (SGD 61) - non-refundable.
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regards,
Consular Section