FYI... just did my 1-year retirement extension today and this is what was required... a TM7 extension form filled out, 1 passport photo, copies of passport identity page, visa page, multiple entry stamp page, last entry stamp page, a copy of lease agreement and income affidavit notarized by US embassy... all copies had to be signed by me. I gave them a copy of my pension statement and asked if could just use pension statement next time, but officer said no, that I needed income affidavit from US embassy.
Man in front of me had Thai bank book & copy with enough monies, but copy wasn't signed & stamped by bank so they turned him away to go do.
Next year will do bank account if exchange rate improves. Would have moved money earlier this year for condo purchase and visa requirements but wasn't sure I was staying. We were hoping wife (was fiancee) would get US fiancee visa but that didn't work out so we were married here and will stay in Thailand.