Have you done both to know?
Maybe things have changed or are different but the last tie I did the marriage extension was in 2015. My daughter and my wife had to also go to the IO as my wife had to be interviewed each time. I tried going one year without them and I was sent away and was told that my wife, at a minimum, had to join me.
I also had to go twice each time. The first to go through the application and interview process, then about 30 days later to get my passport stamped after Bangkok approved the extension.
Yes, 2 copies of everything for marriage and only 1 for retirement, (Writer's cramp signing 2 copies of all the dead trees.) Here's the list of what was required for marriage and has never been needed for retirement. (Maybe things are different now or are different at other IOs):
- Marriage cert
- Divorce decree
- Wife's Thai ID
- Wife's house book
- Daughter's birth certificate
- An affidavit from the US Consulate stating that I was previously divorced, currently married to my Thai wife, and when/where my daughter was born. (NOTE: This affidavit came at a cost. If memory serves me correctly it was $50 USD).
- Pictures of me and the family at our rental home