Koh Lanta in KrabiMultiple islands make up Koh Lanta. Getting to this location from Phuket Island requires either taking to the sea by a boat or driving your vehicle (motorbike or car) on multiple ferries to reach the last of the islands. It is located in Krabi province and is the southernmost island in the area. It also sits near Trang province on the border of southern Krabi. From Phuket, the island is about 74 kilometers over water or 253 kilometers (4.5 hours) drive from Patong Beach.
Your ultimate destination, the longest and last island in Koh Lanta, is 22 kilometers long and about 4 kilometers wide. If you decide to visit this island, there is a wide choice of package tours you can purchase. Probably a much better trip than taking a vehicle on the roads all the distance would be to take a ferry from Phuket, which will get you there in about ten hours.