It would be my guess that they want him to go to his embassy to get an affidavit. He is German. The German embassy still issues affidavits.
Buriram Immigration is not moving to Ban Kruat. The Ban Kruat story is that they are going to have a border checkpoint there that can be used for exit and entry to and from Thailand. Two immigration offices will remain. One in City Hall and one near the stadium. It seems that the City Hall is the main one and fully staffed during office hours. I have never used the one at the stadium so am not sure about staffing levels there.