Need Advice Travelling from Kho Phangan to Bangkok?

I just checked the Air Asia website out, on the 29th of July they have a flight going from Surat Thani, to Bangkok at 8 pm arriving to Bangkok at 9 pm for 699 baht, (around 21 USD dollars). If you are flying out of Samui, there are a ton of flights, but you are looking at 2200-2900 baht one way. I wouldn't take any other mode such as a bus for many reasons, mainly because you could potentially put yourself in danger of missing your morning flight just to save a few bucks on getting to Bangkok.