@Kevin **********
, Face it, you won't be the first foreigner who did this and it's not the end of the world and it doesn't affect your ability to enter thailand at all
BUT
If you don't do your 90 day report (which is due BEFORE you fly out) when you do come back and go to do that 90 day report, they'll see your exit stamp was AFTER the due date of your previous report and fine you the 2000baht for failure to file on time. The fine is 2000 baht whether you're 8 days late or 8 months late so don't worry
AND you'll get a stamp like this in your passport