You can qualify to receive Old Age Security pension payments while living outside of Canada if one if these reasons applies to you:
you lived in Canada for at least 20 years after turning 18
you lived and worked in a country that has a social security agreement with Canada. The time you lived or worked in that country and Canada must be at least 20 years
If you do not qualify to receive your Old Age Security pension while outside of Canada, your payments will stop if you are out of the country for more than 6 months after the month you left.