What should I do if my 90-day reporting for my Thai visa is still pending after filing online?

They only went back to work today after five days off. Give them a couple of days to catch up

Maybe you had the old version of online 90 days report. I logged mine 90 days with app it was pending for a week. Then I went to immigration office at CM. They had notice with a QR code to scan for new website. Looks like it was updated in May 2022.

Theoretically you can file your 90 day report at whatever office you have a TM30 for.

Since you're in Samui you should have a TM30 from your hotel or landlord, so take that to the Samui immigration office with your passport and last 90 day report slip and see if they will let you do one.

Or if you'll be back in Bangkok by the 30th, your window to file in person is up until 7 days after your due date