I know initial Retirement Visa Extension required B800K deposited for 3 months prior to issuance but I am under the understanding that subsequent annual renewals only require the 800K balance to be maintained for 2 months prior to expiration.  Is this correct?

(Understanding that balance can not fall below B400K at any point.)

It was changed to 2 months on date of application for every extension on March 1st of last year.

That is when the requirement to keep the 800k baht in the bank for 3 months after the day you apply and then after that 400k baht for the remainder of the year went into effect.

If you opt to use an agent to show the 800k in your account because you don't want to bring it into the country, are you screwed in a year's time?

29 minutes ago, Promula said:

If you opt to use an agent to show the 800k in your account because you don't want to bring it into the country, are you screwed in a year's time?

You could use agent again or if borders were open without quarantine you could border bounce and enter visa exempt and obtain non O with 800k in bank on day of application and then couple months later apply for annual extension.

35 minutes ago, Promula said:

If you opt to use an agent to show the 800k in your account because you don't want to bring it into the country, are you screwed in a year's time?

Not if you use the same agent, they are quite used to roll over extensions without funds in place. Don't ask how because you will get a considerable amount of comments re legality, but it works so don't knock it.

2 hours ago, ubonjoe said:

It was changed to 2 months on date of application for every extension on March 1st of last year.

Not all offices concur with this, some still insist on 3 months before.

I've never experienced a problem with this as my 800k+ is there year round, but others have enquired of Phetchabun IO and been told there's no change its 3 months before for all extensions. 

11 hours ago, Promula said:

If you opt to use an agent to show the 800k in your account because you don't want to bring it into the country, are you screwed in a year's time?

Use the agent again..... consensus of opinion is that once an agent is used to bypass the money in the domestic bank account for a retirement extension, you are locked in. If you tried to do it yourself next year, they would expect you to demonstrate you did have the 800k a year ago, retained it for 3 months etc etc....... but you didn't. 

Getting a new Non-Imm-O entry  might be a work around.