Would note a couple of minor points:
(1) I really don't know if CM Immigration requires a very recent transaction in your passbook. Because I read a couple+ years back that other immigration offices were requiring that, I've been depositing 100 baht into my "visa account" just in case. But, Jbifl's post seems to say it's now required here in CM and that may be the case.
(2) I was going to switch my "visa account" to Bangkok Bank a couple of years back until I read many posts about BB taking 1-5 days to get the one-year's bank statement from Bangkok; however, Siam Commercial Bank (at least the CM Thaphae office) does both at the same time and generally it takes about 15 minutes. And SCB does stamp and sign each page of the one-year bank statement. As usual, I get those documents and do the deposit thing the day before the retirement extension application. (one needs to make sure the deposit is made just prior to the bank doing their paperwork so your bankbook amount and bank letter amount are the same).
(3) It's been a year or so since I got a re-entry permit here but last time they wanted in addition to the usual paperwork a copy of my TM30 and a copy of my TM47 Receipt of Notification. Never had to supply those before (but, since I take the proverbial kitchen sink with me, I was prepared).
(4) I got my last retirement extension a month ago and, for whatever reason, they wanted a copy of every filled-out page of my passport, including Vietnam stamps. Again, I was prepared as they asked for the same thing about 5 years ago.
(5) Be prepared to be required to give them a photocopy of your original Non-O visa stamp (even if it's in a prior passport). Occasionally, they'll ask for that (regardless if you provide a copy of the transfer of stamps information in your current passport).