Just went to the office, filled out a form, then they cancelled one visa, and started another. I lost about two weeks on the old visa, but no big deal. My Wife was present also, and, for some strange reason I could not figure out we needed a letter from the local Amphur office to say we were still married......don't ask me why. Oh, and the money in the bank. As Proton mentioned, they prefer it as less work for them.
Sorry, I forgot to mention the standard paperwork as listed by MJCM above.