BKK to Khao Lak

WE will be spending several days in Khao Lak & would like to know if bus travel there from BKK. direct is possible.? Where would you catch the bus? & how much for 2 people.Preferably a VIP.coach. Is flying a better option? Any ideas? Many thanks in advance.

Fly to Phuket (1.5hr from BKKf) for 1800 Thb then bus or taxi (1 hr);
or bus all the way maybe 14hrs. I would go to the BKK Southern bis terminal and buy a ticket.

rent a car