THat's not the same - Yu can for instance pay for fast rack on London eye. You pay to have the checks and everything done before hand and some capsules have spaces allotted. However with Thai arrivals everybody has to go through exactly the same process as each other - so the only way they can do that is take someone off the regular city and take away from ordinary arrivals and deliberately create a slow lane to make money for the officials operation the system.
Still corruption - create a slow line and then sell tickets round it. THey are doing exactly the same job as the slow line.
Nepotism corruption an graft in Thailand is grossly underestimated by visitors and you demonstrate why it thrives - over 60% of the Thai population think it's OK.. I personally would certainly reporting it or asking for an explanation.
I prefer the Chaiyaphum route, it is more rural. However, you need to check Google for flood warnings regardless of which route you take. Chanoegsao is nice,
I would stay clear of the BKK hinterland on any route - presumably you have Google set up on a data plan? It's not the fastedt but you get to see more Thailand