By Plain

The small Sihanoukville Airport (IATA: KOS | ICAO: VDSV) is located 17km to the east of town, on the edge of Ream National Park. However, the airport's only scheduled service, between Siem Reap and Sihanoukville on PMT Air, has been suspended after a fatal crash in June 2007. The runway is being extended and international flights may be offered by the end of 2007. 

By bus

From Phnom Penh: National route 4 from Phnom Penh to Sihanoukville is one of Cambodia's best roads. There are regular bus services with Sorya and GST from Phnom Penh (Central Market) which takes about 4 hours at a cost of 15000 Riel, or US$4 through a guesthouse. The first bus leaves at 7:15 AM, the last one at 2:30 PM, and the Snooky terminals for both companies are a few metres apart on Ekareach St. It's worth reserving the day before or at least a few hours in advance to be sure of a seat. Mekong Express also runs two buses a day for US$6, as does Capitol Guesthouse.

From Koh Kong / Hat Lek (border crossing with Thailand): for the most part this road is unsealed and the condition depends on the weather and frequency/scale of maintenance. "Local" and "Tourist" minibuses service this route; they are always jam-packed, and the trip can be uncomfortable. "Local" service price depends on how much space you want (a whole seat, half a seat, or a space on the roof); foreigners can expect to pay around US$6-8. The journey involves four ferry crossings; the scenery is mixed, but does offer some moderately spectacular views at the Koh Kong end.

By taxi

A chartered taxi from Phnom Penh's Central Market can do the trip in less than three hours and will cost anywhere from US$25-40, depending on the gas price of the day and how beat up the vehicle is. You can reduce the price by sharing seats, but be warned that Khmers will squeeze in as many six people into the car, so most people will need to buy two seats for comfort.

By boat

From Koh Kong / Hat Lek (border crossing with Thailand): weather permitting, a daily fast ferry departs from Koh Kong for Sihanoukville at 08:00 and from Sihanoukville for Koh Kong at noon. The journey usually takes about 4-4.5 hours and stops once to pick up/drop off supplies at an outlying island; tickets for foreigners cost US$12 (or 500 baht). Minibuses and moto-taxis shuttle passengers from the ferry to the border crossing; a moto-taxi should cost 50 baht. On the Thai side, minibuses run to Trat (110 baht), direct to Laem Ngop (for ferries to Ko Chang), and direct to Bangkok. If taking the minibus to Trat, note that you will arrive at 18:00-19:00 by which time the only long haul bus services are to Bangkok. In some circumstances it's worth spending a night in Koh Kong or Trat.

By train

There are no longer any passenger services on the Phnom Penh to Sihanoukville railway line. It may be possible to hitch a ride with the freight train security guards - enquire locally for further information.

Get around Central Sihanoukville

Central Sihanoukville Distances between the beaches are a little too long to walk comfortably, but getting around is easy, as the roads are wide and bike taxis (motodop) are everywhere. The standard price is US$1 per trip, although expect to haggle at night or if the distance is long. They'll gladly pile on two people and their luggage too. For larger groups, car taxis can be called up by phone (flat US$5 to most places around town) and there are a few tuk-tuks lurking about too

http://wikitravel.org/en/Sihanoukville