Siem Reap to Koh Rong is never one vehicle. You get to Sihanoukville first, by flight, night bus, or private car, and then you take a boat to the island. There is no airport on Koh Rong you can fly into. Air Cambodia’s booking form, with the origin set to Siem Reap (SAI), does list Sihanoukville (KOS). Giant Ibis lists a night bus it times at 11 hours. A private car is the third way, and it can drop you at a hotel or at the pier. The boat is a separate ticket. On 22 October 2026 we could not confirm a ferry timetable or a fare on an operator’s own site, so this page does not invent one.
Short answer
If you want the island the same day, look for a morning flight from SAI to KOS, leave time for the drive from the airport to the port, and only then buy the boat once you know which beach it serves. If you would rather not connect anything, take Giant Ibis overnight and ride a boat the next morning. A private car sits between those two: you leave when you want, you stop when you want, and you still finish on the mainland unless the driver is handing you to a confirmed boat.
Weather changes what “the beach” feels like. The month-by-month guide is about Siem Reap’s dry and green seasons, which is the half of this trip you already know. The coast is a different sky. Book the boat for the week you are actually travelling, not for a season chart copied from a blog.
Flying Siem Reap to Sihanoukville (KOS)
The airline we could confirm on its own site is Air Cambodia. On 22 October 2026 the destination list for origin SAI includes “Sihanoukville (KOS)”. That is the mainland airport, not Koh Rong. We could not open a timetable with flight numbers or a block time, so this page does not say the hop is 45 minutes or an hour. Search SAI to KOS on the airline and read the result. Fares are not printed here.
KOS is not the ferry pier. You still need a car from the airport to the port. We could not confirm a kilometre figure for that hop on an official airport page, so we are not printing “20 km” from a third-party map. Ask the hotel or the transfer how long they need, and do not book a boat that leaves before that car can arrive.
The same rules as any SAI departure apply on the Siem Reap end. The airport guide puts the terminal about 40 km east of town, 45 minutes to an hour by car, and says to leave 2.5 to 3 hours before an international flight. A domestic hop to KOS can be tighter, but the drive to SAI does not get shorter. A “morning flight” that you miss because the hotel car left at sunrise-tour time is not a morning flight.
Air Cambodia’s Phnom Penh airport in the same booking form is Techo International (KTI), not the old in-town code people still type. If you are building this trip as Siem Reap, then Phnom Penh, then the coast, use KTI when you search the Phnom Penh flight. The road version of Siem Reap to Phnom Penh is a separate guide, linked below.
Overnight bus
Giant Ibis’s Siem Reap to Sihanoukville page lists the duration as 11 hours. It does not list a distance we are willing to repeat: the page also says 60 km, which cannot be an 11-hour highway, so ignore that distance. The bus is a night service. Complimentary pickup is not available. You get yourself to the terminal behind the Old Stadium, Khmer Pub Street. On board, the crew hands out water, a pillow, and a blanket. The night buses have an onboard toilet, and the page says the bus does not make bathroom stops. Drivers swap during the night. The page describes that stop as about 15 minutes.
The arrival line on the page is mislabelled. The heading says “Arrival in Phnom Penh.” The address under it is the Giant Ibis ticket office on Phe Street, Sangkat 3, Sihanoukville, next to the Sihanoukville Autonomous Port. Use the address, not the heading. Tuk-tuks wait there. That port adjacency is the useful part: you are already beside the boats, not across town.
We did not confirm Vireak Buntham, Saly VIP, or any other company on their own sites, so they are not named as options. If you book a different bus, read where it actually stops. A Sihanoukville drop that is not at the port costs you another ride before the ferry.
Private car
Two private transfers were the Sihanoukville run when we checked Viator on 22 October 2026. Neither of them is a boat ticket. They end on the mainland.
Cambodia Taxi Driver’s “Private Taxi Overland Transfer From Siem Reap - Sihanoukville” was 5.0 from 19 reviews, from $111.99. The listing includes gasoline, tolls, parking, and the expressway fee, and it can drop you at a hotel or at the pier. It runs in both directions. Vehicle choices are an SUV for 1 to 3 people (a Lexus or a Highlander) or a minivan for 4 to 7. The published duration is 8 to 10 hours.
Siem Reap Shuttle’s “Private Transfer : Siem Reap ↔ Sihanouk Ville” was 4.9 from 13 reviews, from $180. The description is a private air-conditioned car, van, or minibus, hotel pickup and drop-off, gasoline included, and a driver for up to 10 hours, with stops for food if you want them. Options are a 3-seater (Camry or SUV), a 6-seater Hyundai H1, and a 10-seater Hiace or Urvan. The web address still says “Private Angkor Day Tour by Army Jeep.” That is a stale slug. The title and the description are the Sihanoukville transfer, and the code in the link is 56250P3. Read the title on the page before you pay. A guide is not included. The listing prices an English-speaking guide at $30 extra if you ask for one.
We did not link a car-and-ferry product whose public web address still says Poipet. Until that address shows Koh Rong on the page itself, it does not belong in a guide that is trying to keep people off the wrong road. Buy the mainland car here, and buy the boat from the company that tells you the beach.
The boat to Koh Rong and Koh Rong Samloem
Koh Rong and Koh Rong Samloem are different islands. A ticket to “the island” is not specific enough. Ask which pier you leave from, which beach you arrive at, and what time that boat actually sails on your date. We could not read a current timetable on GTVC, Speed Ferry Cambodia, or Buva Sea on 22 October 2026. One domain that third-party pages treat as a ferry company resolved to an unrelated site. Because of that, there is no departure clock, no 30-to-60-minute crossing, and no fare on this page.
What we can tie to a source is the bus arrival: Giant Ibis stops next to the Sihanoukville Autonomous Port. Start the boat conversation there, or with the hotel on the island, and match the beach name to the booking. If you are staying on Samloem, do not accept a boat that only mentions Koh Touch on Koh Rong unless you have a second hop you trust.
Breaking the trip in Phnom Penh
The coast is a long way from the temples in one sitting. Splitting it in Phnom Penh is the version that lets you sleep in a bed. The Siem Reap to Phnom Penh guide is the first leg: bus, flight, private car, or the seasonal boat. From the capital, Giant Ibis’s Phnom Penh to Sihanoukville page lists 240 km and 4 hours, leaving from Street 106 at the Night Market, with a pickup from partner hotels and a 30-minute stop at a rest area on the expressway. That is a different bus from the 11-hour Siem Reap night service. You are adding a city, not saving the whole day.
A flight via Techo (KTI) is the other split, if Air Cambodia is selling both SAI–KTI and KTI–KOS on your dates. Check both legs on the airline. We are not printing a connection time.
A Kampot boat
Some travellers reach Koh Rong from Kampot instead of Sihanoukville. We could not confirm a daily boat, a pier, or a crossing time on an operator’s site, so this page does not describe one. If a guesthouse in Kampot offers the ride, ask them which beach it uses and get it in writing. Do not plan the Siem Reap day around a Kampot departure we could not verify.
Temples, then the beach
The usual order is Angkor first and the island after, because a salty rest day is easier to enjoy once the sunrise alarms are finished. The honeymoon guide is the Siem Reap half of that trip: where to stay slow, and which evenings are worth dressing for. Then use this page for the exit. Give the coast at least two nights if the journey is the 11-hour bus. One night on Koh Rong after an overnight bus is a shower and a boat back.
FAQ
Is there a direct flight from Siem Reap to Koh Rong?
No. There is no airport on Koh Rong you can fly into. Air Cambodia’s booking search offers Sihanoukville (KOS) from Siem Reap (SAI). You still take a boat from the mainland to the island.
How long is the bus from Siem Reap to Sihanoukville?
Giant Ibis lists the night bus as 11 hours. It leaves from behind the Old Stadium on Khmer Pub Street, and the night bus does not include a free hotel pickup. We could not confirm other operators’ times on their own sites.
Which way is faster, the flight or the bus?
The flight to KOS is the shorter trip when a boat is still running after you land. We could not confirm the airborne time on the airline’s own timetable, so we are not printing one. Giant Ibis’s bus is the 11 hours on its route page, overnight, and the ferry is still a separate ride the next day.
How long is the ferry to Koh Rong?
We could not confirm a crossing time or a fare on a ferry company’s own site on 22 October 2026, so neither is printed here. Giant Ibis stops next to the Sihanoukville Autonomous Port. Ask the boat which beach it uses before you pay.
Can I get from Siem Reap to Koh Rong in one day?
Only if your flight lands in time for a boat that is actually sailing, and you already know which beach you are staying on. The night bus arrives the next morning, which avoids a same-day connection. Do not book the island night on the assumption a specific afternoon boat will wait.
What is the difference between Sihanoukville, Koh Rong, and Koh Rong Samloem?
Sihanoukville is the mainland town and the port. Koh Rong and Koh Rong Samloem are two different islands. The private-car listings on this page end in Sihanoukville. Tell the boat which island, and which beach, you actually want.
Bus details were read on giantibis.com on 22 October 2026. The flight note is Air Cambodia’s booking list the same day, not a timetable. Ferry times and fares are omitted because no operator site we opened would confirm them. Check the boat on the day you travel.