What documents are needed for a marriage-based visa extension in Thailand?

Congratulations, now first things first, do you have a Thai bank account in your name only with bt400,000 in it for at least the last two months, or at least two months before you apply. Without this you can not get a type O visa/extension based on Thai wife. If, and when, you have this then there are documents you also need that are not on that list:

One of the sets of your original marriage certificate and registration certificate. You should have gotten two.

Copy of your passport. I copy every page as it speeds things up.

A copy of your wife's ID card, front and back.

A copy of the house book your wife is listed in. She'll know what this is. (Your #3).

If you rent where you live then a copy of your lease with your name on it, and the name of the property on it. Some use a generic lease without the property name on it, and isn't accepted by immigration.

If you rent then a copy of the owner's ID card front and back, and a copy of the house book they're listed in.

A set of 4x6 pictures of both of you in front of the property you rent showing the street number. A picture of both of you in front of your entrance and showing the room number if there is one. A few pictures of both of you inside where you live.

A hand drawn map showing how to get to where you live from the closest main road.

Now finally, last but not least, and the most important, two letters from your Thai bank. One showing that it is in fact your account in your name only, and then a second letter showing your balance for at least the last two months. Three months is better. A copy of your bank book data page, and at least the last two months of your bt400,000+ balance . Your bank book is also updated on the day you apply.

Oh, and a passport photo of you.

That's it.

Make copies of everything, as everything is the same for next year with just updated bank letters and all new pictures.