Andy You can use money in your home country for an O-A visa but the O-A has an insurance requirement. There are several ways to get an O visa which is a 90 day visa with no insurance requirement. Eventually getting 1 year extensions of stay will require money in a Thai bank.
You can’t meet the financial requirements. Do you mean the 800,000 baht banked money method or the monthly income method? Any chance you can begin saving the money?
The bank letter states you have an account and states the balance at the time of the letter. A bank statement is just what you think it is. The history of your transactions over a period of time (3 months, 6 months, 1 year)
It is likely you may be required to do a withdrawal or deposit same day and then have your bank book updated
You should probably mention which immigration office you are using. Are you seeking an extension based on retirement or marriage. Are you using the income method or banked money method.
It sounds like the income method. It is a simple test. Are you depositing the minimum amount (or more) into a Thai bank account only in your name.
Also, if you choose to continue using the monthly transfer method the money needs to be deposited in a Thai bank account. If you can afford the banked money method that is easiest. Make sure you get a non-immigrant O visa. Not an OA.