How can I meet the income criteria for a retirement visa in Thailand without embassy proof of income?

So I guess it is safe to assume you would have to continue to show 800k baht in your Thai bank account for every 12 month extension unless you do as Brandon suggests by transferring at least 65k every month.?

Just transfer 65k each month from overseas into a Thai bank account. I've done it that way for years

For the initial non-O visa and the first 1-year extension, it's not an option. You would have to use 800,000 baht in your Thai bank account. During this first year you could start transferring at least 65,000 baht per month to your Thai bank account that just show as an international transfer. The 2nd year you can use proof of 12 monthly transfers as proof of income, and then withdraw the sum you need for the extension the previous year.