What are the requirements and costs to extend a Non-Immigrant O Visa to one year in Thailand?

To meet the financial requirements on a yearly extension of stay based on marriage you'd either bank 400K baht in an account in your name only for 2 months prior to you applying for the extension (and yes you CAN open a bank account without a work permit, you're just checking with the wrong bank branches) ;)

OR

You get an notarized affidavit of income from abroad from your consulate here stating you get 40K baht a month income. That's the ONLY thing you can use to prove income (unless you're legally working here and use thai pay stubs and thai tax receipts).