If you don't have 15 days or more left on your current entry stamp you need to apply for a 30 day extension for 1900baht THEN apply for the 90 day Non-O visa right after that.
As
@Barry **********
suggested, GO out to the immigration office at Chaengwattana Road and get the hand out from the section that sells 90 day in country Non-Immigrant visas (Section C-1). That will give you the list of documents you need to apply for that visa.
You show up, apply, pay the 2000baht, it will go under consideration for 14 days then you go back out there with your receipt and passport and they ink in the new Non-O visa & a new 90 day entry stamp.
THEN you wait until you have 45 days or less left on that new stamp and go back to apply for the yearly extension based on marriage. This is when the money needs to be in the account in your name only for 2 months before you apply for the extension.