Khao Lak remains somewhat inaccessible, which is part of its charm for many people. The beach lies about 80 kilometers (50 miles) north of Phuket, which is the closest airport. There was talk of building an airport in Phang Nga province, but these plans where shelved after the December 2004 tsunami wiped out much of the tourist infrastructure in the area.
For now, the best way to get to Khao Lak is to fly to Phuket, then arrange for ground transfer to Khao Lak. Many of the better resorts offer complementary transfers from Phuket airport. If you want to arrange your own transportation, a limousine service from the Phuket airport will set you back 2,500 Baht (64.93 USD). There's also a van service, which costs about 800 Baht (20.78 USD). However, Phuket taxis have a bit of a reputation problem, with many reports of stops at tour agencies and other rip-offs. I've heard good things about Khao Lak Taxi, which has competitive rates for airport transfers.