Can't help about Chaiyaphum specialized money exchangers if any.
Commercial banks offer rates that are about 0.3 worse than best money exchanges.
Would end with 3000 Baht less for 10000 Dollar.
And the banks can be quite picky about clean crisp notes, denying any notes with dog-ears, scribble etc. Go to main branches only. Passport required.
Whether it's worth a trip to Khon Kaen where you might get 0.2 better than at a bank in C.P.? (there are money exchangers).