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You wait it out, THEN apply once that visa is no longer valid for entry to thailand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)
You might want to get the 90 day Non-O visa from the thai consulate in your country before you wing your way here although you will be fine applying for the in country 90 day Non-O with a passport that expires in July 2027.
Your passport will not expire within the time you will get on the Non-O visa OR the year extension (figuring from Aug, that's 90 days so about November 2025, and then a year extension is Nov the following year (2026)
Your passport expires 8 months AFTER that year extension (so you'd renew the passport before you went to get the second year extension Nov of 2026)
Machine Readable Zone, it's that set of numbers letters on the bottom of the data page of your passport, you scan that and the system auto fills in the data (but it gets it wrong a LOT of the time and if you submit an application with a data entry error it's cancelled and you lose your funds)
You need to keep the 800K baht in the bank account for 3 months after your yearly extension is granted and after that the balance can't go below 400K for the rest of the year (before you get it back to 800K 2 months before your next yearly extension
You should GO to your immigration office and get the hand out listing the requirements for the yearly extension based on retirement at that specific office well before you're going to go for the extension, that way you know what copies, documents, bank letter, statement, updated bank book, map, photo, etc you need to get together