Believe me
@Bob *********
you are far from the first foreigner who forgot to do a 90 day report within the 21 day window you have to file one in person. 😕
The upside is there's no need to race right over to the immigration office because the fine is a fixed 2000baht and that's whether you're 8 days late or 8 months late. As long as you get it sorted out BEFORE your next extension is due you will be fine.