By train
There are no 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. As of autumn 2010, there are efforts to make the Cambodian railways operational again. Since October 2010, a freight service from Phnom Penh to halfway Sihanoukville Touk Meas is operational.
By plane
Sokha Helicopters (http://www.sokhahelicopte...) offers a VIP charter service between a private helipad at Sokha Beach Resort and Phnom Penh and Siem Reap. Charter rates start at US$1495 per flight hour plus 10% VAT & 10% SPT, with discount packages for stays at Sokha Beach Resort. Helicopters are modern, French-built Eurocopter Ecureuils with luxury leather seating for 5 passengers. Licenced pilots are from Australia and Europe. Flight time from Phnom Penh is 55 minutes and Siem Reap 1 hour and 40 minutes.
By taxi
A chartered taxi from Phnom Penh's Central Market can make the trip in less than three hours and will cost anywhere from US$25-40 per car, depending on the petrol 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 as many as eight people into the car, including two in the drivers seat, so most people will need to buy two seats for comfort.
By bus
Phnom Penh Sorya Transport (http://www.ppsoryatranspo...), GST Express, and Mekong Express operate hourly bus services from Phnom Penh, taking 3-5 hours and costing US$4.5-10, depending on the quality of the bus and the number of stops. The first bus leaves Phnom Penh at 7:00AM; the last bus leaves at 5:45PM. All buses arrive and depart from the bus station downtown near the Central Market. Tickets can be booked at the bus company offices, travel agencies, and many guesthouses. It is worth reserving a day in advance to be sure of a seat. National Route 4 between Phnom Penh and Sihanoukville is one of Cambodia's best roads.
Rith Mony, Bun Thou, and Virak Buntham Express operate daily air-conditioned minibus service leaving at 8:30AM to/from the the border with Thailand at Koh Kong/Hat Lek, taking about 5 hours. "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. They will also typically have pickup in front of the offices on the main strip in town at 7:30AM at which point they simply drive over to the station to wait until the 8:30AM departure time. You may be offered pickup at your hotel for a premium. Sometimes there are buses leaving at 2:00PM but the service may be available only with suitable demand and ticket prices may be higher ~US$15.
In 2010, Virak Buntham Express started a bus service from Ha Tien in Vietnam to Sihanoukville via the new Xa Xia/Prek Chak border post. From Ha Tien, there is a ferry to Phu Quoc island, another popular tourist destination. Unlike even recent travel guides report, this trip now has become easy and straightforward. Visa on arrival for USD 25/550.000 VND but bring a photo!
By ship
Boats used to run daily from Koh Kong/Hat Lek the border crossing with Thailand, taking around 4 hours and costing US$20/700 baht. However, the service was suspended in 2008 and it's unclear if it will resume, since travel by road is now cheaper, safer and just as fast. Several sources quote "persistent rumours" about a future ferry service with the nearby Vietnamese Phu Quoc island, but nothing happened yet.
Modest numbers of cruise lines offer one-day port visits, usually along with more stops in Vietnam enroute to or from Bangkok, e.g., Oceania.