I'm kind of obsessed with documenting this.
So here is everything you have to do, if you're married to a Thai national and want to extend your stay for another year.
Documents needed for one year extension of marriage visa – sorted in official Chaeng Watthana order (as far as I observed)
Completed TM 7 form with one passport sized photo glued to the form on page 2: https://bangkok.immigration.go.th/wp-content/uploads/2021/06/14คำขออนุญาตเพื่ออยู่ในราชอาณาจักรเป็นการชั่วคราวต่อไป-ตม.7.pdf
Completed STM2 form: https://bangkok.immigration.go.th/wp-content/uploads/Form-STM2.pdf
Statement form handed over by immigration, that your wife will have to fill out. - Can't find a download link for this one.
Acknowledgement form for overstay penalties: https://bangkok.immigration.go.th/wp-content/uploads/Form-Acknowledgement-of-Overstay-Penalties.pdf
Copy of your latest TM30 receipt / Copy signed by you
Passport: Original (of course)
Copy of passport personal page / Copy signed by you
Copies of all passport pages with Thai stamps on it / All copies signed by you
Bank letter for 400 kTHB – Example for Bangkok bank: https://aseannow.com/topic/1044527-sample-bank-letter-for-retirement-visa/#comment-13108657 – Chaeng Watthana wants it on the same day than the application day, but accepts one day before as well. Best do it in Bangkok bank branch in Chaeng Watthana and pay 100 THB into the account beforehand, update the bank book and make copies of it.
Bank book: Original
Copies of updated bank book after bank visit on application day / All copies signed by you
Marriage certificate – Original
Marriage certificate copy / Copy signed by your wife and you
Updated Kor Ror 2 (Your wife needs to do get one 1 or 2 days before the appointment)
Copy of ID card of your wife / Copy signed by your wife
Copy of tabien baan (blue book) of your wife / Copy signed by your wife
Colour photo of your wife and you inside the living room glued to an A4 paper sheet signed by your wife and you
Colour photo of your wife and you at unit door entrance with room number visible glued to an A4 paper sheet signed by your wife and you
Colour photo of your wife and you at condo entrance with house logo and/or street number visible glued to an A4 paper sheet signed by your wife and you
Drawn map to your condo or house from the main street signed by your wife and you
Copy of the rental agreement / All copies signed by your wife and you
Copy of ID card of your condo owner / Copy signed/certified with condo owner signature
Extension fee of 1 900 THB
Recommended reserve documents just in case – only hand over when asked
A signed copy of the condo/house owners' tabien baan (blue book) for the rental property
Colour photo of your wife and you in front of the kitchen glued to an A4 paper sheet signed by your wife and you
Colour photo of your wife and you inside the bedroom glued to an A4 paper sheet signed by your wife and you
Further advice
Bring your own blue pen, glue stick and scissors just in case you need to correct something
Useful: Download page for all immigration documents: https://bangkok.immigration.go.th/en/downloads_en/
The under consideration period is now just three weeks for the 2nd time. So I will be able to pick up the final year stamp on 31.01.2024.
Pink line to Immigration and back
We used the pink line. So upon arrival, there is taxis waiting below the station. We picked one and turned left into the 2nd road, that goes all the way to the immigration entrance. The first road is Chaeng Watthana Soi 7 and the station is about in the middle of those two access roads.
On the way back my wife asked and the shuttle departs from the middle entrance and exit, gate 1. Since the building is called B, it is the gate B1. From there the free shuttle took us to the beginning of Chaeng Watthana Soi 7 in about 5 minutes. Then it's just a 2 minute walk to the Pink Line station.
Personal comments
My wife always has to go and make copies of about half the documents after they have been stamped by immigration. I presume it is the same for everyone under the marriage visa.