What is the process and cost for renewing a retirement visa in Khon Kaen, Thailand?

I will do it for $50

If you are fit and mobile you realy should try to get your extension yourself. It's not just the money you will save but also the multitude of issues that could cause you problems later on. For example if you get a new passport your local office will not transfer your stamp. You will have to go to the office that issued your stamp. It realy is not duffucult and if you present yourself well at immigration the officers should be very helpful. It would help you to get what is required from your bank if you get an IO to write out in Thai what they want to see.

Go to immigration at Khon Kaen and ask for a list of the requirements.

As mentioned, if you have already had the retirement visa for 12 months , the renewal & requirements should be 1900 baht

1900 baht is the rate you pay at Immigration.

You do not need an agent to do this for you.

1900 baht...

You are applying for an extension of stay based on retirement? Not a visa?

Why do you need someone to do it for you if you have the money in the bank?