Hi- I missed my regular 90-day reporting due to having a new baby and the COVID situation (the online/app options never worked for me) and now we are getting ready to move out of Thailand this month. Is there a way to take care of this and pay the fee at the airport before leaving? Or if I leave without taking care of this, what is the worst thing that happens next time I try to enter the country for a visit (which will definitely happen since my husband is Thai)? Thanks in advance for any help on this!

Immigration at a airport have nothing to do with 90 day reports. You can just leave the country and they will not say a word about it.

Same when your return to the country.

and when you re-enter thailand it resets the 90 day count

If you really want to do it (for peace of mind), there is a Post Office at Suwannaphum Airport.  Of course, you would not receive the receipt, unless there is someone remaining at your residence.

40 minutes ago, allane said:

If you really want to do it (for peace of mind), there is a Post Office at Suwannaphum Airport.  Of course, you would not receive the receipt, unless there is someone remaining at your residence.

That would not work since she has already failed to do a 90 day report.

No problem to leave and re-entry after not doing a 90 day report.