What should my wife do about her overdue 90-day report in Chiang Mai due to COVID concerns?

No disrespect intended but, it wasn't the "right thing to do", the 90 day report was due, she did not do it and now she's more than 7 days late.

Chiang mai allows mail in 90 day reporting as long as it's post marked 14 days before the due date, SO that was an option as was going to either the drive thru (without getting out of the car) or going to the Promenada Mall.

At this point i's a cut and dried 2000baht fine for failure to file a 90 day report on time.

Just go when ever you're gonna go. The fine is 2000baht whether you're 8 days late or 8 months late.

2k is the maximum fine

The fine remains at 2,000 Thai baht. No increases. Pay later when she needs to get a service from Thai immigration.

>If she waits does the penalty increase (other than the 5,000 fine if she is arrested)? Or does anyone have a better idea?

The penalty won't change; it'll be 2K THB the next time she does something at immigration.