What bank statements do I need for my Non-O visa extension application in Thailand?

Are you talking about your very first extension of stay or a second extension of stay? If the former you only need 3 months worth of statements, if the latter the statements at least must go back to the day you received your previous extension

You cannot renew a visa. You can apply for an extension. Each extension is its own brand new application, so there is no renewing anything.

You say this is your first extension? That means you are finishing up your 90-day non-O visa? If that's the case, then you just need to show that the money was in your account for 2 months, so a 3-month bank statement will work. YOU cannot produce this. The bank has to provide an official bank statement to you. You'll also need a bank letter.

Go to your immigration office and ask them for their list of handouts of requirements for an extension of whatever type you need (since you don't say what your non-O is for). That will have the specific requirements for YOUR office, since each office sets their own requirements.