just because you've never seen it doesn't mean it hasn't been posted about many times. But most people that start with agents don't want to stop regardless. And there's nothing theoretical about what I've posted. Many posts of people accidentally dropping their account below 400,000 and bringing it back up in the same day and they still got denied their extension and had to start over. I don't know why you think showing 0 in your bank account after using an agent would be any different than 399,950.
they would absolutely be refused for one of two reasons.
1) their previous stamp is from some immigration office in the middle of nowhere, hundreds of kilometers from where they live, and that office is known as one that agents take their customer's passports to get sketchy extensions. They will straight up be told by the immigration office that they cannot get their extension their and will also likely be told to use an agent again.
2) as part of using an agent they did not have the required funds in their Thai bank account. The requirements for an extension based on retirement are that you need to keep the 800,000 in your account for 3 full months after receiving the extension, cannot drop below 400,000 ever, and must be back at 800,000 for 2 full months before they apply for their new extension. As part of their extension application they must show 12 months of bank statements that show they met this requirement for last year's extension. If they used an agent to bypass that requirement, they won't be able to show that they met the requirements and they will be denied a new extension for failure to meet last year's requirements.
If your stamp is from your local office and you can show that you've had the required funds through the previous year then you should be okay to get your extension on your own.
We are. 90 days is the visa, the 1-year is the extension. You cannot switch between the 90 days and the 1-year extension. Sounds like you probably used an agent so it doesn't matter regardless.
Depends on the immigration office. Some require you to file a new one if you travel around Thailand and some do not. You need to check the rules for your local office.
Did you get the non-O from a Thai embassy before you traveled to Thailand, or did you convert to the non-O visa at an immigration office in Thailand?
If you got the non-O from an embassy you can move wherever you like.
If you got the non-O from Thai immigration, then no other immigration office will issue you a 1-year extension of stay except the office that you obtained the original visa from. Once you have the extension you can move wherever you like.