My wife and I are US citizens.  We each entered Thailand with a Non-Immigrant O-A retirement visa in April 2016.  We are preparing for our first 1 year extension of stay as our current stay expires in February 2018.  I have a notarized letter from the US Embassy with my pension information and a seasoned Thai bank account with the required 800,000 Baht if needed. My question regards the extension for my wife, specifically what documentation will she need to show adequate funds.  Will a copy of my notarized pension letter and a copy of our marriage certificate be sufficient?  If not, what is needed?  I would rather get an extension for her instead of a dependents visa, if at all possible.

If she needs her own, independent, retirement-extension, she will have to have her own pension-statement meeting 65K/mo or the 800K seasoned for the requisite time in a bank-account in her name only (no joint-accounts), or a combination of the two (only in her name) totaling 800K for the year (pension per/mo X 12 + bank-balance).

43 minutes ago, Zuman said:

I would rather get an extension for her instead of a dependents visa, if at all possible.

She would not get a dependent visa at immigration. She would get a extension of stay as your spouse after you get yours and it would expire on the same date as yours. No need for financial proof for her application.

Got it.  Thanks.

3 hours ago, Zuman said:

I would rather get an extension for her instead of a dependents visa, if at all possible.

You could use your pension income for your extension, and put the 800K in an account in your wife's name for hers. The 800K will need to be in the bank for 60 days.