I probably know the answer to my question but I'm hoping I'm wrong:  my 90-day report for my retirement visa (Samui immigration) is due May 22.  I fly out to my home country on May 26.  The re-entry permit is already in my passport.  As I officially have a week, until May 28, to file the report, will there be a problem if I just skip the report this time?

I would do the the report just to be safe. There is always a chance that immigration would fine you for not doing the report before leaving.

There will be no problem.

 

You don't need to report your address as you're leaving (albeit temporarily) the country. You cannot be fined on exit or anytime in the future for not reporting.