I echo all the other very positive reviews. A fellow Cruise Critic person booked 8 of us on a 6 hour tour of the island. We came in via tender from the Sapphire Princess. It took a little work to connect with Mr. Chicken (he WAS there with the sign on the dock). 10 person vehicle is clean with good AC (critical), and he was very conscientious to either keep the van running or go out early after lunch to get it cooled off for us.
He suggested an itinerary to see many of the sites on Ko Samui. We adjusted a little bit at the end, but he was always willing to make any changes that we wanted. The price per couple was better than reasonable for the day. He stopped for lunch at a place called Sabienglae, where he's wells known and got us great, quick service. Lots of fresh seafood choices and fresh drinks (separate review).
They have an office at and perhaps family affiliation with Crystal Bay resort, which looked wonderful when we stopped for a view.
Highly recommend for a private tour of the island!