If you get the non-O from outside of Thailand then travel to Thailand, in order to apply for the 1-year extension the 800,000 must be in your account for 2 full months already on the day you apply for the extension.
Once you receive the extension, your bank account must remain at 800,000 for 3 full months, and then it can never drop below 400,000 the rest of the year.
Next year, you must bring it back up to 800,000 for a full 2 months before you will apply for the extension.
Repeat every year. It's much easier if you just leave it at 800,000 all the time so you don't have to worry about when to deposit the money to bring it back up to the required amount.
The money is not for your living expenses, it is for emergencies to show the government that you will not become their problem if something bad happens.
I don't know what a "reduced" retirement visa is. Are you asking about the amount of money required in the bank?
A marriage visa/extension requires 400,000 in the bank. This is not a retirement visa, it's a marriage visa.
A retirement visa has nothing to do with being married, the requirement is that you are over 50 years old. The required funds in the bank if using that method is 800,000.
every immigration office has their own requirements. That's why you MUST go to YOUR immigration office and ask them for their list. As an example of making it difficult, Chiang Mai immigration will only accept proof of the 500k in a Thai bank account. Yes, they know DTV people cannot get a Thai bank account. That's the entire point.
You're not going to find information about DTV extensions here. You must go to immigration and ask for their list of requirements. If they're even willing to give you a list, expect new items to be required that are not on the list each time you return to the office. Their goal is to make it so difficult and annoying that you leave Thailand. They'll even tell you that's the best option. 99% chance that's what you end up doing because immigration wants nothing to do with the DTV.
First of all they didn't close your account, they froze it.
Second, they did it to everyone, even people that already verified their information. Multiple reports of people that went in and provided everything then frozen again the next week. They had to go in and show everything again.