Living out the end of your life won’t fit on a stamp. Also maybe they just got worn down over the years by people calling it a ‘retirement visa’ and just caved in?

In my opinion, the fees for overstay are not really what they should be paying. If they've admitted the fact that they've caused this problem they should be paying all your expenses to go and get another visa so that you don't have to overstay.

Don't overstay your visa!

Non imm O-A

Not a non imm O

After the visa itself has expired, but the permission to stay stamp is still valid, if you want to leave the country and keep it valid, you would need a re entry permit.

To be honest, two years is reasonably long term for visas in Thailand. I mean you can go for the Elite card if you can afford it but it's quite a lot of money up front.

Yeah, they're good at confusing :)

No, you do all the financials in your home country.

Volunteering is classed as work as far as visas and work permits are concerned so you won't be able to do that on an ED visa either.

Seeing as you're planning to move full time to Thailand, as long as you meet the requirements, I would recommend getting the Non-Imm O-A from a consulate or embassy in your home country before you arrive.

Once you do arrive, you will be stamped in to Thailand for a whole year, and if you exit and re-enter the country just before the 'use before' date on the visa you will be stamped in for another year, giving you almost two years in the country.

Whilst you find your feet and decide what you want to do and where you want to live, I think that this is the most hassle-free option for you, after the initial hassle of actually getting it that is :)

Maybe

To keep your current permission to stay valid, if you want to leave the country and re enter during that permission to stay, what you need is a re entry permit. It is attached to, and has the same length of validity as, your current visa or extension of stay. It is not a separate visa itself.

In your case, with your single entry visa, if you enter Thailand on that visa, but want to travel and return during the permission to stay that that visa gives you, you purchase a re entry permit before you travel either at an immigration office or an airport. This permit will then allow you to travel and return to Thailand at which point you will be stamped in again for the remainder of your original permission of stay.

Once the visa you have the permit on expires, the permit expires with it.