@Wy***
and
@J**
there are TWO different steps you take to get from a tourist visa or a visa exempt to a "marriage visa".
FIRST you apply for an in country 90 day NOn-O visa based on marriage to a thai (that cost 2000baht). When you apply using banked money there is no seasoning requirement (meaning the money doesn't need to be in the bank for any set amount of time) BUT it does have to be transferred in from abroad into a thai bank account in your name only.
You apply for this visa and it will go under consideration for between 2 and 3 weeks depending on the immigration office (Bangkok is 14 days Chiang Mai is 21) then you go back, get the Non-O visa inked in and a new 90 day stamp.
When that new 90 day stamp runs down to about a month left on it you go back to the immigration office and apply for the year extension of stay based on marraige for 1900baht . This step is the one that requires the 400K baht be 'seasoned' in your account for 2 months before you apply for the extension. When you apply you'll get a 30 day under consideration stamp (and some offices say you need to keep the money in the bank during that time too) and then you go back and get the year extension inked into your passport. After that you can spend the money as you want to.