What are the financial requirements and options for extending a Non-Immigrant Visa O-A in Thailand?

This post is in regards to one year Extension of Non-Immigrant Visa category O-A and not the original visa. Bangkok Bank NYC will require American banks to utilize the international (IAT) ACH format starting April 1, 2019 to move money to Thailand. This may make it problematic or costly for some Americans to move the money to Thailand here on a monthly basis.

One of the current options to meet financial requirements of the O-A extension in lieu of the income affidavits is a letter from your Thai Bank certifying your account and showing an 800,000 THB balance to meet the financial requirements. For those that have already used this option for their extension, how long do the funds need to have been deposited before applying for the extension of stay (not the original visa)? Once your extension is approved are there people that have used the 800,000 THB for their monthly expenses and they just repeat the process again for their next extension in a year? Or is the money required to stay in a Thai savings account for the entire year earning a fraction over 0% interest?

The other option is to deposit at least 65,000 THB into your Thai bank account each month. Are there some that have just ensured that they deposit 65,000 THB cash (from a business, or an ATM withdrawal from their bank back home, etc) into their Thai bank account instead of directly transferring the money from their home bank to their Thai bank? I am not suggesting that you deposit and withdraw the 65,000 THB each month and recycle the money which may be obvious to Thai immigration.