I plan on going to the U.S. Embassy and get a notorized statement of my annuities. But I won't be able to go to thai immigration about a week or so later. To renew my retirement visa. Would the notorized letter still be valid or would I have to apply for another statement?

Have not seen anyone post about being turned away with a week old pension letter so think you will be ok.

I agree with Lopburi, one week will be fine.

After a month or two you might have problems.