What is the duration and validity of a NON O e visa for Thailand?

There are 2 time periods to be aware of.

First is the validity of the visa. A non-O visa is valid for 90 days from the day it is issued. That means you must enter Thailand within 90 days which is the date written on the visa.

Second, will be your entry stamp. Once you enter Thailand you will receive a 90 day entry stamp. After 90 days you must either leave or apply for an extension. You don't say what type of non-O visa you have so I'll assume it's for retirement. For a retirement extension you must have embassy certified income of 65,000 baht per month or 800,000 baht in a Thai bank for 2 full months from the date you apply for your extension. That means if you're using the money in the bank, you only have about 30 days to get your bank account opened and get your money transferred into the account, or you'll run out of time to apply for your extension.