I'd bet dollars to durian you don't have any valid visa 😉 but instead are here on an "extension of stay" based on being the spouse of a foreigner on a legal visa/extension.
All you're doing is a REASON CHANGE from one extension to another
The seasoning requirement on banked money method for extensions of stays based on retirement are "the funds need to be in a thai bank account in your name only for 2 months before you apply for the extension, then the 800K stays in the account for 3 months after the extension is granted and after that the balance can't go below 400K baht the rest of the year
You would get everything ready for the retirement extension (all the documents, bank letter, statement, updated bank book, map, copies, lease TM30, etc) go in cancel your extension based on being a trailing spouse (you might or might not need the primary visa/extension holder with you to cancel the current extension you're on as it's just a piggy back one)
As soon as you cancel the current extension you'd apply for a new yearly extension based on retirement for 1900baht
GO to your immigration office, get the hand out listing the requirements for the extension based on retirement well before you're going to try this change the reason for an extension.
You are far from an idiot 🙂 but with that being said you sure picked a tough immigration office to deal with 😮 🙁
AND
You're probably way ahead just going to Samui and trying
BUT
if it doesn't fly there and you are running out of time just bounce you out and back by land to get a new 180 day stamp (There are services that run almost every day to the border from Samui)
That would lead me to believe that they'd run out of time on their current stamp BEFORE they could get an appt at that renegade office there on the "Island of Misfit Toyz" aka Koh Phangan 😉
you do not want to submit the data until you have that whole application filed out, and that means, proof of your location (that you're in Lao) proof of funds, CHECK the data that the MRZ auto filled when you scanned your passport, etc
It's not a race, 🙂 get it right (y) check it carefully, THEN submit it once you have it complete and ready to go
You'll get the confirmation (which you need to PRINT) and then you go to the consulate to pay for the visa (showing that print out to get in the gate)
Doubt you're on ANY real VISA and it's much more likely you're actually here on an "extension of stay" based on education <- LOOK at the stamp in your passport it should say "extension of stay permitted until" and have a date you can stay until
You can just leave on that stamp, go get a DTV and come back without any issue at all
No need to go to the immigration office and cancel it before you leave
the real question would be WHY did you burn your 180 day entry stamp down so far before you went to the immigration office ?
At most offices in the country you can apply for a new extension of stay when you have 30 days or less left on your current stamp (and you don't lose any time applying early because the extension is added to your current expiration date)
There actually is NO requirement at all as far as passport validity to get a new yearly extension at your immigration office.
Works like this
IF your passport isn't valid for the full year you would get when you apply for the extension you only get the extension issued until your passport expires. 😮 Then you'd get a new passport and apply for a new yearly extension on the new expiration date
As far as your question your extension if you apply for a new yearly extension at your immigration office in Dec for an extension that runs out in Jan you'll get a stamp good until Jan 2027, Your passport is valid longer than the extension you'll get