If you mean that without having deposit in your Thai bank accout, yes, you can get a single entry Non-O visa for retirement purpose from Royal Thai Embassy, London with deposit in a bank account in another country.
But if you mean in ANY bank, no you cannot unless you can provide financial evidence showing monthly income of no less than 65,000 THB (£1,500).
Please check the requirements for Non-O retirement from RTE London here.
Yes, you have to (if your local office requires you to submit TM.30 again after returning to the same address in Thailand).
TDAC and TM.30 are different systems. TDAC is about the record of arriving in Thailand, and the address in TDAC is about the place you are going to stay. TM.30 is to report that you are actually staying at that address.
You can go any day to do a 90-day report at the local immigration office between 15 days before and 7 days after the due date (in case you will do it in person at the local office).
You may be fined if you miss the 90-day report, but you will not receive any "bad mark" in your passport even if you fail to report within 90 days anyway.
Draw a map from the nearest landmark. It could be a part of checking that you are really living at the location. It depends on your local immigration office whether they accept Google Maps or not.
If you are on ED-plus extension, you are supposed to be able to apply for working (non-b, non-o working for organizations, or perhaps non-rs) without leaving kingdom. Why not talk with your local immigration office and your employer in future.
If you cancel your extension, you have to leave within the day as ED-plus cannot have future data to terminate the extension.
You need to have funds of 800k baht in your Thai bank account for full 2 calendar months as of application day for a new one-year extension. Some offices ask for 3 months instead of 2 months.
“3 months after the extension granted” is counted from the day you get your new extension stamp at many offices. But there are a few offices that count “3 months after” from the day your new extension starts.
You need to check the province specific detailed policy with your local immigration policy.