There are no successful posts about people with valid MULTI-ENTRY VISAS who applied for a DTV before their previous visa expired
The people who said they applied for a DTV had a single entry tourist visa <- which meant the stamp cancelled when they exited, AND the people who said they got it from an ED visa, really had an "extension of stay" from the immigration office here <- which is not a visa
You cannot hold two valid VISAS in your passport at the same time, you'll get denied
IF you have a 6 month METV you wait for that visa itself to expire before you apply or you'll get your DTV application rejected
You wait it out, THEN apply once that visa is no longer valid for entry to thailand
as Jan said you have 3 months from the date they issue the Non-O visa to ENTER thailand and even if you came in on the last day the visa is valid for you'd still get 90 days when you stamped in
getting a new yearly extension doesn't reset the 90 day reporting at all, it just runs, the only thing that resets it is exiting/coming back into the country
SO
if you arrived back in the country on the 6th of April your 90 day report would be due July 4th
You have to do the first 90 day report when you come back into the country IN PERSON (you can try online but people are getting their reports rejected with this notice in the email
If it was the FIRST yearly extension based on retirement, they usually put a small paper in your passport telling you when your first 90 day report is due
LOOK and see if it's stapled to one of the pages (sometimes under the receipt)