How can i go from bangkok to krabi?

By air or by land. You can fly a number of airlines to Krabi two of them being Air Asia or Thai Airways. You can also take a bus to Krabi. If you plan to take the bus don't go with one of those tour buses. Take a bus from the southern bus terminal. You can take a night bus VIP 24 seat or 32 seat leave about 8 pm and arrive about 7 or 8 am the next day. Cost about 900 baht depending on which type bus you take.