For a start inspections are NOT carried out "Thoroughly ". Having just one person inspecting, never using jacks and levers, tapping every visible nut with a small ball peen hammer, depleting air tanks, until the audio alarm goes off, timing how long it takes to recharge the air, check the gauges ......
Then the the other problem is they inspect all buses in the same months, how daft can you get, the correct way would be to have an appointed Date and Time as in the UK (was/is) not just turn up Ad Hoc. and spread the inspections across the whole year.
If the bus companies are paying up to 8K a year in Bribes, then charge MORE for the inspections and employ more TRAINED Staff, it 'aint rocket science.
If the so called Transport Minister stopped his concentration on Airports to appease the Tourist industry, and spent more time addressing the Driving tests, road carnage, and sorting this mess out then things could improve. He needs a consultant from the real world HERE in Thailand from IMO the UK. But Thais know best, init.