When is my first 90-day reporting due after extending my Non-Immigrant O visa in Thailand?

@David ********

actually that's NOT correct :( the O/P got their first yearly extension AND they didn't notice that the immigration office had put a paper in their passport stating when they do their FIRST 90 day report

After they looked thru their passport they found the slip telling them when they do their first report

@Henrik ***

90-Day Reports and extensions are not related, I agree. However, if every time you get an extension of stay immigration staples a new 90-Day Report Receipt/Next Appointment Date into your passport you can be forgiven for thinking they sort of are. I don't know if this goes on at other immigration offices but it's been going on for 8 years in Phuket. ;-)

@Kool ******

In my experience of 8 years in Phuket this is not true. When I apply for a retirement extension my passport comes back with the retirement extension stamp and a new 90-Day Report Receipt/Next Appointment Notice. I honestly can't remember this not happening. They don't discuss it, ask me if that's what I want. It just happens. I notice it when I check my passport after having it returned to me. I can't say whether this happens at other immigration offices or not.

No problem, glad you found it! I always check mine after they give it back because in December 2020 I went through the "Drive In" at Phuket and they forgot to change the year to 2021 and said I had to report back sometime in March 2020!!!