What are the steps to convert a Non-B visa to a Non-O visa for marriage in Thailand?

Okay, Jason Matthews you are confusing getting an EXTENSION based on marriage inside tthe country with getting a Non-O visa based on marriage outside the country

Lets go thru this step by step what you can do to get the year extension inside the country (IF you have the 400K baht seasoned the full two months before you apply to switch your extension reason.

FIRST get all the documentation required to apply for a yearly extension of stay based on being married to a thai <- which most likely will entail you and your thai wife going to the immigration office and getting the hand out that lists the requirements.

Make sure your 400K baht is seasoned the 2 months BEFORE you are go to try to do this

Take your employment termination paper AND the proof you cancelled your work permit to the immigration office cancel your current extension based on employment IMMEDIATELY apply for a NEW yearly extension based on marriage (by meeting the requirement) You should get a 30 day under consideration stamp and then you go back on that date and get the year extension inked into your passport

PLEASE, giving advice is nice BUT...... There is no need to get every piece of paper with your name on it certified, translated, stamped by Ministry of Foreign Affairs, local police, notaries and who every you think is important enough to stamp.. NO, you still do not need the attendance records of your kindergarten classes, signed and notarized.

There are two ways to get an Extension of Stay: Hire a big truck, a few strong guys and bring each and every document with your name on it, make sure you have at least 10 copies of each one and tell every one, that this is required by yourself.

OR

Visit the Immigration Office, ask the latest and updated hand out with requirements, tick the list when copy made or pictures are printed.

Stop with this endless listing of documents and telling what ever Immigration Officer wants to see you bring.

You could potentially apply for a 90 day non-o in country which can then be extended. But do the funds not have to come from overseas for this?

This could potentially be of help - I did the exact same thing in Chiang Rai a few years ago, and also didn't quite have time for the funds to season in the bank account. If you have a thai child, they let me use a 60 day extension for the purposes of 'visit thai child' in between the work extension and the marriage extension as a spacer while the funds seasoned. When that 60 days was up I made the switch to a marriage extension, by which time the funds were seasoned

First visit your local Immigration Office to ask the hand out with requirements for an Extension of Stay based on married to a Thai National.

Get all these requirements done, make sure you do not miss one.

Cancel the Extension of Stay based on working

Apply directly for a NEW Extension of Stay based on married with a Thai National

if you apply for the 7 days refusal of extension you will HAVE to leave the country