Very convenient. Koh Samui Airport is really small. Walk 50 meters from baggage claim to the exit, and you'll see 4-5 car rental service points in a row. The last one on the end is the rental company, very easy to spot. The car had 27,500 km on it but was well maintained. Everything went smoothly throughout the process. Since the car return point was not at the airport exit, I drove directly to the departure area, parked on the side, called them (with the help of a nearby staff member), and they came to pick up the car within 5 minutes. The car inspection and return process took just 1 minute.