How do I calculate the 90-day report deadline for my Thai Non-O visa extension?

The 90 days report has to be filled 90 days after you last entered the country or 90 after the last report you did. It’s not related to when you got your visa or extension but to the date on your entry stamp.

You literally have the next 90 day report paper on the right side of that picture, what does it say?

Is this the FIRST yearly extension you've ever gotten on the Non-O visa?

I ask because they put a paper in your passport when you apply for that first extension (when you got the under consideration stamp) that tells you when your first 90 day report is to be filed,

Go thru your passport page by page (look under the blue green stapled receipt etc) and see if you have the paper in there

it looks like this