If I purchased an SRS annuity plan, and the payout is set for 20 yrs for $1k per month starting at 65, what happens to the subsequent payout after 10yrs since SRS needs to be withdrawn within 10yrs from 62?

After 10 years, SRS account is deemed closed. You'll be taxed at the remaining surrender value at the 10th year of your policy. So if you still have a surrender value of 100k, that'll be taxed at 50%. Then future payouts won't be taxed anymore.

Also you only need to withdraw within 10 years from your first withdrawal. So if you start at 65, it's only at 75 when the account is deemed closed.