Getting in Sihanoukville
The small Sihanoukville Airport (IATA: KOS | ICAO: VDSV) is located 17km to the east of town, on the edge of Ream National Park. Cambodia Angkor Air started flying to and from Siem Reap on December 14th, 2011 with three flights a week. They also fly nonstop to and from Vietnam (Ho Chi Minh City) 3-4 times per week. There are red-eye flights from Beijing (PEK) as well now. AirAsia began flying to and from Kuala Lumpur, Malaysia in August 2017, 4 times a week. Hainan Airlines offers direct service to KOS from BaoAn Airport (SZX) in Shenzhen, China.
Sokha Helicopters  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. Licensed pilots are from Australia and Europe. Flight time from Phnom Penh is 55 minutes and Siem Reap 1 hour and 40 minutes.
Sihanoukville is a famous destination for holidays for both locals and foreigners, there are many buses and minivans going there every day and the road is usually in good condition. You can check the different schedules, prices and book directly online via camboticket.com
Cambodia’s rail network has recently been restored and provides a cheap and comfortable way to travel. Services between Phnom Penh and Sihanoukville restarted in April 2016. Tickets cost $7 each and the journey is more relaxing than the bus trip. The service is operated by Royal Railways.
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 driver’s seat, so most people will need to buy two seats for comfort. As of May 2013, you can get a private taxi to Sihanoukville for $60 – $65. Many of these have an LPG tank in the boot, so two large cases are the limit. If two people travel a spare seat can cater to a second large case. Most of the cars are relatively recent Toyota Camrys and comfortable enough. Order from Travel Agents around the city or taxi service online.
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.
Boats to the islands offshore – Koh Rong and Koh Rong Samloem, run every day several times per day. You can take a slow boat, speed ferry, or make a day out and go on a tour boat. Speed Ferries are the best option if you just want to get out to the island as quickly as possible, as the company runs a modern purpose-built catamaran with lots of undercover seating. Alternatively, get on a day trip tour boat and you should be able to use your ticket to get off at the island and stay overnight and return another day.
Modest numbers of cruise lines offer one-day port visits, usually along with more stops in Vietnam en route to or from Bangkok, e.g., Oceania.