@Gary ********
There's also a third option, leave Thailand and re-enter after the OA runs out, but re-enter on Tourist visa or visa exempt. Then apply for the 90 day Non-O inside Thailand. But this one has an added requirement that you must be able to show that the 800,000 was transferred from overseas.
If you apply for the 90 day Non-O outside the country, you meet the requirements they want there, but then when you go for the 1 year extension in Thailand, you just have to show that you've had 800,000 in a bank for 2 months, not where it came from.