I'm going at the end of November, it's more cost effective to drive to Karon from Bangkok, air fares are ridiculous, cabs to and from the airport is 2000bt hiring a car on the island for a few days works out a lot more than driving, plus we get to see the countryside on the way down.
Be aware that if you don't have a Visa the Airline may kick up, Austrian were about to refuse me in April ( I slipped up because Thailand cut the 45 day exemption back to 30 days and I didn't have time to apply online) I was able to explain that I had an appointment at Petchabun immigration two days after arriving and provide evidence, then they waived the rule, it was touch and go for 20 minutes though