When should I apply for my Non-O Retirement visa extension in Chiang Mai and what documents do I need?

Why wait until 10 November? I would do it today

Bank passbook updated same day yes but not enough. You also need one year bank statement. And I would suggest go early if you can. The extension will be from Nov 20th, in any case, even if you go 30 days before.

Following

Go to the office and get a print out of what they need, they all seem to differ.

You should make a trip to the office and pick up the application form and any other forms they require as every office seems to have different rules. You will need some passport size photos. For instance, Phuket has some declaration forms about overstay. They require a small transaction on the day you apply and your bank book updated to show that transaction and a copy of it. Your bank guarantee letter is usually good for a week. Phuket immigration gave me a packet of documents I needed to fill out and sign, along with a list of other items they require including a copy of every Thai stamp in my passport.

In Chiang Mai you can apply anytime from 45 days before the end of your current stamp, up until the day it expires. How close you want to let that run is up to you. You will probably need a bank statement as well as the bank letter and bank book copy.