Does the 90-day reporting period start from my arrival date or the retirement visa stamp in Thailand?

You should have a note they stapled into your passport with your 90 report date. Or at least that's what they did for mine

You may mix some things. If you applied for Non-O before you entered Thailand and stamped in for 90 days, it is Non-O based on retirement/being over 50. What you applied for inside Thailand at the local immigration office is a 1-year extension based on the same reason, not a visa anymore.

Now, the first 90-day period for the report count starts the day you applied for a 1-year extension at many offices. But some offices might count from a different day. Please check your passport again, You may have a note about the first 90-day report due.

On the other hand, if you were already on 1-year extension and enter Thailand with re-entry permit, 90 days start on the day you arrive.

You get 90 day, after another 12 month will start so totale 15 months

The 90 days starts with your date of arrival into Thailand.