@T**
don't mix up the requirements to get a VISA from a thai consulate outside the country and the requirements to get a yearly extension of stay from the immigration office inside the country. Those are whores from different go-go bars :O Sorry I mean horses of a different color (I mix up my metaphors sometimes :( )
For the extension you bank the 400K baht in a thai bank account in your name only for 2 months before you apply for a yearly extension OR you go to your consulate and get a notary letter stating you get 40K baht a month in income OR if you legally work here with a work permit you show 3 months of tax statements showing you get over 40K baht a month. Those are the only ways to meet the financial requirement to get a yearly extension of stay inside the country at the immigration office.