How many days after the 90-day due date can I leave the country without being penalized? My due date is Friday 16 August, and I fly out some time that weekend.

Thanks

Just exit.

No TM47 is checked at airport.

Also you are within the requirement dates for reporting

 

Thanks DrJack54.

Just beware, however, that the first 90-day report due after your return to Thailand will, as things currently stand, have to be submitted in person or by snail mail (i.e. not online), as referred to in other recent threads.