I will be arriving at BKK in March at 4:20pm. I need to get to Krabi ASAP. Same day if at all possible. I found 3 flights departing at 6:25(Thai Airways), 6;45(Thai Viajet and 7pm Bangkok Airways. Will be separate tickets. Is the 7pm flight doable? Would Fasttrack service be advisable? How much is Fasttrack?