Mark Robert stated in another thread
After 7 consecutive annual extensions of stay based on marriage and a 400K cash deposit, this year I will unfortunately miss the cut-off time for the 2 month seasoning of the 400K deposit. Therefore, I will most likely need to apply for the " 60 day visit my Thai wife extension for 1900 baht without showing any banked money" as mentioned above. What documents and which form are required in order to obtain the 60 day extension?
TLDR : Answer Summary
To apply for a 60-day extension based on marriage to a Thai citizen, you will need to prepare the following documents: your marriage certificate, your wife's Thai ID, the house registration book (house book), and the TM.7 application form for extension. It's advisable to submit your application a few days before the expiration of your current extension.