Just go to bus stop and take a Van. From Ao Nang to Krabi it takes some 30 minutes and 40 paths. It's fast when it get going, but normally the drivers are waiting the car full (about 10-14 persons) before leaving town. And no use to go to bus stop they are stopping if they just think that you need a ride. (Imagine Toyota Hilux with plastic roof and 15 persons in the platform).
There's many renting offices in front of the Ao Nang main street. Take one, you have to leave your passport or money to guarantee, but the prices are low. Remember to be careful out of there, the traffic is hectic, left sided and there can be a lot of drunk people, especially on the evenings and nights.
Ao Nang is very easy to get to by car with a good paved road from Krabi.
We had a rental car that we picked up at the airport.
It is obvious from the sticker on the back window, that we rented it from Budget .
I wish they wouldn't announce the fact that we are tourists.
Ao Nang is pretty small and you can walk almost everywhere in 20 minutes! The walkway along the beach stretch is very nice at night and there are plenty of big sidewalks to walk on. Be careful at crosswalks (zebras) though because not all drivers will stop for you.
My friends were staying at the Krabi Resort on one side of Ao Nang and I was at the Aonang Villa Resort on the other side. I don't know how many times I walked back and forth with no problem! You can also window shop along the way or better yet, you can speak to some of the local residents and make new friends like I did!!!
If I would have been scooting around in a vehicle I probably would have missed half of the great little shops and craft stalls around Ao Nang. Walking is really the best option when the weather is good :)
But if you aren't much into walking, take one of the little Tuk-Tuks. You should be able to get one for around 40THB, if you are going a bit far they will up the price to around 60THB. You can also rent a motor-scooter if you are going to do a LOT of running around but if you are a diver like me and are just going out at night, it's probably a waste of money.
If you need to go somewhere further like the National Parks, you can most likely rent a van & driver from the hotel. We rented one from Krabi Resort and paid about 600THB for the entire day to go to the National Parks.