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Cheap flights from London Heathrow Airport to Siem Reap from £375

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 4/9. Fares are subject to change and may not be available on all flights or dates of travel.
LHR — SAI
7 Sep — 14 Sep1
1 adult
1 adult, Economy, 0 bags

Cheap flight deals from Heathrow to Siem Reap

Enter your travel dates to find the best prices.

Cheapest flights from Heathrow to Siem Reap
Explore the most affordable flight options available from Heathrow to Siem Reap. Find the lowest fares from popular airlines and budget airlines, with prices last updated on 8 August 2026.

Thu 3/1206:00 -
2 stops29h 45m
Mon 14/1209:55 -
2 stops29h 25m
Deal found 3/8£577
Thu 3/1206:00 -
2 stops29h 45m
Mon 14/1209:55 -
2 stops18h 45m
Deal found 3/8£605
Fri 25/906:00 -
2 stops30h 55m
Tue 29/909:40 -
2 stops28h 15m
Deal found 4/8£613
Tue 10/1109:05 -
2 stops26h 40m
Thu 3/1209:55 -
2 stops18h 45m
Deal found 3/8£614
Sun 20/906:00 -
2 stops30h 55m
Sat 3/1009:40 -
2 stops18h 05m
Deal found 3/8£615
Wed 2/912:10 -
2 stops24h 45m
Wed 30/916:00 -
2 stops22h 40m
Deal found 3/8£625
Mon 16/1117:30 -
2 stops33h 20m
Mon 7/1209:55 -
2 stops29h 10m
Deal found 4/8£629
Wed 2/906:00 -
2 stops30h 55m
Wed 23/909:40 -
2 stops18h 05m
Deal found 3/8£630

Find flight deals from Heathrow to Siem Reap

Keep the following information in mind while searching for Heathrow to Siem Reap flight deals. Data was last updated 8 August 2026.

Round-trip from

£577

One-way from

£375

Popular in

December

Cheapest in

July

Average price

£926
Austrian Airlines
  • Austrian Airlines
  • 3/12-14/12
  • 4 total stops
  • 59h 10m total
  • London to Siem Reap
Search Deals
4/9
  • 4/9
  • 2 total stops
  • 37h 55m total
  • London to Siem Reap
Search Deals
Highest demand for flights based on searches. 11% potential increase in price (£74 potential increase over avg. return price).
Search Deals
Cheapest flight prices on average. 4% potential price decrease (£27 potential savings vs. average return price).
Search Deals
Average for round-trip flights in August 2026
Search Deals

Cheapflights Fare Finder

 
Customise your flight search to find flights from Heathrow to Siem Reap that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 858,174 searches. Data last updated 8 August 2026.
Use the filters below to find and compare flights from London Heathrow Airport to Siem Reap that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest return flight

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Mon 16/11

11:00-16:55

1 stop22h 55m

Siem Reap–Angkor Intl

Mon 7/12

18:40-07:15

1 stop19h 35m

£832

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Thu 3/9

18:55-21:05

1 stop20h 10m

Siem Reap–Angkor Intl

Mon 28/9

19:40-17:50

1 stop28h 10m

£863

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Tue 10/11

11:00-17:40

1 stop23h 40m

Siem Reap–Angkor Intl

Sat 5/12

21:30-07:15

2 stops40h 45m

£932
Fastest return journey

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Wed 19/8

18:55-17:10

1 stop16h 15m

Siem Reap–Angkor Intl

Wed 16/9

18:05-08:35

2 stops20h 30m

£940

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Fri 25/9

07:30-17:10

2 stops27h 40m

Siem Reap–Angkor Intl

Tue 29/9

18:05-16:55

1 stop28h 50m

£961

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Mon 4/1

11:00-19:40

1 stop25h 40m

Siem Reap–Angkor Intl

Wed 20/1

18:40-07:15

1 stop19h 35m

£979

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Mon 31/8

18:55-17:10

1 stop16h 15m

Siem Reap–Angkor Intl

Fri 11/9

18:05-10:30

2 stops22h 25m

£1,070

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Tue 10/11

06:25-16:10

3 stops26h 45m

Siem Reap–Angkor Intl

Thu 3/12

19:25-16:20

2 stops27h 55m

£1,078

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Mon 4/1

11:00-16:55

1 stop22h 55m

Siem Reap–Angkor Intl

Wed 20/1

17:55-08:20

2 stops21h 25m

£1,110

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Mon 17/8

18:55-17:10

1 stop16h 15m

Siem Reap–Angkor Intl

Sun 23/8

18:05-17:05

1 stop29h 00m

£1,142

Flights are sorted by cheapest return flights first.

Deals found on 4/8

Showing 1-10 of 20 resultsSorted by cheapest first
1
2

Best time to book a flight from Heathrow to Siem Reap

Have a flexible travel schedule? Discover the best time to fly to Siem Reap from Heathrow with our price prediction graph.
Estimated return price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

Everything you need to know about your flight from London Heathrow Airport to Siem Reap

No data available for this route at this time. Please check back soon.

Reviews of airlines servicing Siem Reap

Get insights into the airlines that provide service to Siem Reap. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Siem Reap. Reviews last updated 8 August 2026.
Get a feel of what it's like to fly with Singapore Airlines,Thai Airways, andVietnam Airlines from London Heathrow Airport to Siem Reap by reading reviews from past customers. You can also see how each airline compares in terms of entertainment options, comfort, food, crew/service, and boarding process.
Singapore Airlines
8.2
Very Good
1,583 reviews
Check prices

Comfort

8.0

Entertainment

8.1

Food

7.8

Boarding

8.3

Crew

8.6

Overall

8.2

Reviews

1 / 20
6.0
Good

Anonymous,Feb 2026

SAI - SIN

The only issue we had was seat selection. Was not easy to change, after they assigned seats. Also, the premium economy seats, are nothing special.. All and all safe flight with minor back issues.
Singapore Airlines
8.2
Very Good
1,583 reviews
Singapore Airlines
8.2
Very Good
1,583 reviews
Check prices

Comfort

8.0

Entertainment

8.1

Food

7.8

Boarding

8.3

Crew

8.6

Overall

8.2

Reviews

1 / 20
6.0
Good

Anonymous,Feb 2026

SAI - SIN

The only issue we had was seat selection. Was not easy to change, after they assigned seats. Also, the premium economy seats, are nothing special.. All and all safe flight with minor back issues.
Thai Airways
7.9
Good
413 reviews
Singapore Airlines
8.2
Very Good
1,583 reviews
Check prices

Comfort

8.0

Entertainment

8.1

Food

7.8

Boarding

8.3

Crew

8.6

Overall

8.2

Reviews

1 / 20
6.0
Good

Anonymous,Feb 2026

SAI - SIN

The only issue we had was seat selection. Was not easy to change, after they assigned seats. Also, the premium economy seats, are nothing special.. All and all safe flight with minor back issues.
Vietnam Airlines
7.7
Good
283 reviews
Singapore Airlines
8.2
Very Good
1,583 reviews
Check prices

Comfort

8.0

Entertainment

8.1

Food

7.8

Boarding

8.3

Crew

8.6

Overall

8.2

Reviews

1 / 20
6.0
Good

Anonymous,Feb 2026

SAI - SIN

The only issue we had was seat selection. Was not easy to change, after they assigned seats. Also, the premium economy seats, are nothing special.. All and all safe flight with minor back issues.
Austrian Airlines
7.6
Good
951 reviews
Singapore Airlines
8.2
Very Good
1,583 reviews
Check prices

Comfort

8.0

Entertainment

8.1

Food

7.8

Boarding

8.3

Crew

8.6

Overall

8.2

Reviews

1 / 20
6.0
Good

Anonymous,Feb 2026

SAI - SIN

The only issue we had was seat selection. Was not easy to change, after they assigned seats. Also, the premium economy seats, are nothing special.. All and all safe flight with minor back issues.

Related info for your journey

Find useful and relevant information for your journey from Heathrow to Siem Reap. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • How long is the flight from London Heathrow Airport to Region of Siem Reap?

    A quick flight from London Heathrow Airport to Region of Siem Reap can take about 22h 55m. Vietnam Airlines provides one of the quickest options available for as low as £832. Airlines will cover a distance of 6106 mi.

  • What are the cheapest airlines to fly from London Heathrow Airport to Region of Siem Reap one-way?

    £451 is the cheapest one-way deal found within the past few days, from Vietnam Airlines. You may also be able to find cheap deals on Singapore Airlines and Thai Airways, with prices starting from £555 and £557, respectively.

  • Can I find deals for flights from Heathrow to Siem Reap that include hotel bookings?

    Yes. In addition to deals on Heathrow to Siem Reap flights, Cheapflights offers holiday packages that include both flights and hotel.

  • How can I find direct flights from Heathrow to Siem Reap?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Heathrow to Siem Reap.

  • Can I find deals for business class flights from Heathrow to Siem Reap?

    Yes. Cheapflights offers flight deals from Heathrow to Siem Reap by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

See more FAQs

Browse thousands of different options on Cheapflights for your next trip

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Top 4 airlines flying from Heathrow to Siem Reap

Discover the top 4 airlines that operate flights from Heathrow to Siem Reap. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 858,174 searches. Data last updated 8 August 2026.
AirlineCheapestAverageFlexibilityOn-time
Austrian AirlinesCheapest£552Average£686FlexibilityNo cancel feeOn-time78%
Search Austrian Airlines flights
Vietnam AirlinesCheapest£615Average£813FlexibilityNo cancel feeOn-time81%
Search Vietnam Airlines flights
Singapore AirlinesCheapest£662Average£781FlexibilityNo cancel feeOn-time81%
Search Singapore Airlines flights
Thai AirwaysCheapest£887Average£1,019FlexibilityNo cancel feeOn-time77%
Search Thai Airways flights

Fly with Cheapflights

Find the best flight deals on Cheapflights, where travellers can enjoy low prices and a wide availability of flights to their desired destinations.

How does Cheapflights help users find flights from Heathrow to Siem Reap?

Cheapflights goes through 900+ travel sites to look for the best flight deals for flights from Heathrow to Siem Reap. Too many options? Cheapflights also provides filters for things like airlines, price ranges, and number of stops to help you make a decision easily.

Why should you use Cheapflights to find cheap flight tickets from Heathrow to Siem Reap?

Cheapflights helps you find that perfect flight to Siem Reap from Heathrow by searching from hundreds of airlines and agencies you know and love. We are also free to use, in case you were wondering!

Can Cheapflights find flights from Heathrow to Siem Reap with no change fees?

Certainly. Search results for flights to Siem Reap from Heathrow shown to you on Cheapflights can be narrowed down with different useful search filters, which includes flexible booking options.

Can Cheapflights notify me if prices for flights from Heathrow to Siem Reap become cheaper?

Yes, Cheapflights offers price alerts on Heathrow to Siem Reap flights so you can book your travel at the perfect time. Price Alerts can be enabled by clicking the bell icon next to the flight deals above and providing your email address where you want to receive the alerts.

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