When is the 90-day report due after entering Thailand or extending stay based on marriage?

please count from the latest (last) date you entered Thailand. From there if your continuous stay is 90 days or above then 90 days reporting is required. If your continuous stay is not 90 days and you plan to leave thailand then 90 days reporting is not required.

getting a new yearly extension doesn't reset the 90 day count down clock (unless when you got the new year extension they gave you a NEW receipt showing when your 90 day report would be due)

Your next 90 day report is due 89 days from the date you stamped back IN to thailand (you can apply in person from 2 weeks before that date until 1 week after that date)

After 90 days continuous stay in the country