It doesn’t say I NEED 800,000 baht, it says I need to prove that I have earnings of 65,000 a month (showing at least 3 months bank statements) OR have at least 800,000 baht in a bank account
And by the way I think you’re wrong about that. Yes you need that information for the EXTENSION but you also need it for the initial entry visa. Once you are in Thailand on that Visa you can apply for the EXTENSION.