Do I need to report 90 days after returning to Thailand if I left with a re-entry stamp?

The TM.47 (or 90-day report)

Is to notify the Thai government of your continued stay within the country. If you leave Thailand during your 90-day report period, it’s void.

Once you come back, your 90 days begins the day you arrive.

For example, if your next 90-day report is at the end of this month (31st Aug) but you decide to visit Vietnam for the weekend, your next 90 days isn’t end of the month, but 89 days when you come back from your vacation.

If you’ve been renewing online and leave the country, your first report back has to be in person again.

First time back to Thai, report in person. Afterwards, online ok.

correct

Leaving Thailand stops the 90 day report. Comming back the 90 days start again.

A 90 days continuous stay in Thailand. So if you return, then yes.

YES

Yes. The “clock” restarts at day one on your return. So 89 days after you enter is your new reporting date.