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Cheap flights from London Heathrow Airport to Siem Reap from £349

LHR — SAI
28 Sep — 5 Oct1
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

Mon 21/921:20 -
3 stops40h 50m
Tue 15/1222:00 -
3 stops50h 30m
Deal found 26/8£619
Sun 8/1106:00 -
2 stops29h 45m
Wed 27/116:50 -
2 stops25h 25m
Deal found 29/8£625
Mon 30/1106:00 -
2 stops29h 45m
Sun 13/1209:55 -
2 stops18h 45m
Deal found 28/8£634
Tue 1/1219:25 -
2 stops16h 20m
Sun 13/1209:55 -
2 stops18h 45m
Deal found 28/8£652
Thu 10/908:45 -
2 stops28h 10m
Wed 7/1009:40 -
2 stops28h 15m
Deal found 25/8£657
Wed 9/922:40 -
2 stops37h 25m
Wed 7/1019:10 -
1 stop27h 45m
Deal found 26/8£657
Thu 10/908:45 -
2 stops28h 00m
Thu 8/1009:40 -
2 stops28h 15m
Deal found 28/8£668
Tue 1/1219:25 -
2 stops16h 20m
Mon 14/1209:55 -
2 stops18h 45m
Deal found 28/8£677
Mon 21/922:10 -
2 stops37h 55m
Tue 15/1220:30 -
1 stop17h 45m
Deal found 26/8£690
Thu 3/1206:00 -
2 stops29h 45m
Mon 14/1209:55 -
2 stops18h 45m
Deal found 27/8£691
Sun 29/1109:05 -
2 stops26h 40m
Sun 13/1209:55 -
2 stops18h 45m
Deal found 28/8£692
Wed 9/913:50 -
2 stops23h 05m
Thu 8/1009:40 -
2 stops18h 05m
Deal found 25/8£696

Find flight deals from Heathrow to Siem Reap

Round-trip from

£619

One-way from

£349

Popular in

December

Cheapest in

July

Average price

£919
China Eastern
  • China Eastern
  • 21/9-15/12
  • 5 total stops
  • 91h 20m total
  • London to Siem Reap
Search Deals
23/2
  • 23/2
  • 2 total stops
  • 43h 10m total
  • London to Siem Reap
Search Deals
Highest demand for flights based on searches. 9% potential increase in price (£64 potential increase over avg. return price).
Search Deals
Cheapest flight prices on average. 4% potential price decrease (£25 potential savings vs. average return price).
Search Deals
Average for round-trip flights in August 2026
Search Deals

Cheapflights Fare Finder

 
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

Thu 10/9

08:45-18:55

2 stops28h 10m

Siem Reap–Angkor Intl

Wed 7/10

09:40-07:55

2 stops28h 15m

£657

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Thu 10/9

18:55-08:45

1 stop31h 50m

Siem Reap–Angkor Intl

Sat 10/10

22:35-17:50

2 stops25h 15m

£766
Fastest return journey

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Thu 3/12

11:00-20:30

1 stop26h 30m

Siem Reap–Angkor Intl

Mon 14/12

18:40-07:15

1 stop19h 35m

£783

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Tue 10/11

11:00-20:30

1 stop26h 30m

Siem Reap–Angkor Intl

Thu 3/12

17:05-07:15

2 stops21h 10m

£786

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Tue 10/11

11:00-20:30

1 stop26h 30m

Siem Reap–Angkor Intl

Sat 5/12

21:30-07:15

2 stops40h 45m

£829
Cheapest one-way

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Mon 22/2

19:50-16:05

3 stops37h 15m

£364

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Wed 14/10

22:00-18:05

2 stops38h 05m

£377

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Thu 21/1

22:00-08:50

2 stops27h 50m

£396
Fastest single journey

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Wed 17/2

19:25-18:45

2 stops16h 20m

£408

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Thu 18/2

19:25-18:45

2 stops16h 20m

£464

Flights are sorted by cheapest return flights first.

Deals found on 27/8

Showing 1-10 of 11 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

Cheapflights Insights

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

What is the cheapest month to book a flight from London Heathrow Airport to Region of Siem Reap?

Currently, March is the cheapest month in which you can book a flight from London Heathrow Airport to Region of Siem Reap (average of £682). Flying from London Heathrow Airport to Region of Siem Reap in July is currently the most expensive (average of £902). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

Reviews of airlines servicing Siem Reap

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
1,589 reviews
Check prices

Overall

8.2

Boarding

8.3

Crew

8.6

Entertainment

8.1

Comfort

8.0

Food

7.8

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
1,589 reviews
Singapore Airlines
8.2
Very Good
1,589 reviews
Check prices

Overall

8.2

Boarding

8.3

Crew

8.6

Entertainment

8.1

Comfort

8.0

Food

7.8

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
417 reviews
Singapore Airlines
8.2
Very Good
1,589 reviews
Check prices

Overall

8.2

Boarding

8.3

Crew

8.6

Entertainment

8.1

Comfort

8.0

Food

7.8

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
286 reviews
Singapore Airlines
8.2
Very Good
1,589 reviews
Check prices

Overall

8.2

Boarding

8.3

Crew

8.6

Entertainment

8.1

Comfort

8.0

Food

7.8

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
952 reviews
Singapore Airlines
8.2
Very Good
1,589 reviews
Check prices

Overall

8.2

Boarding

8.3

Crew

8.6

Entertainment

8.1

Comfort

8.0

Food

7.8

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

  • 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 28h 10m. SWISS provides one of the quickest options available for as low as £657. Airlines will cover a distance of 6106 mi. When browsing for deals, the options you’ll see will be for both direct flights and flights with stops.

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

    £375 is the cheapest one-way deal found within the past few days, from Austrian Airlines. You may also be able to find cheap deals on Vietnam Airlines and Singapore Airlines, with prices starting from £447 and £499, 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.

  • What is the cheapest month to book a flight from London Heathrow Airport to Region of Siem Reap?

    Currently, March is the cheapest month in which you can book a flight from London Heathrow Airport to Region of Siem Reap (average of £682). Flying from London Heathrow Airport to Region of Siem Reap in July is currently the most expensive (average of £902). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

Browse thousands of different options on Cheapflights for your next trip

Top 4 airlines flying from Heathrow to Siem Reap

AirlineCheapestAverageFlexibilityOn-time
Austrian AirlinesCheapest£534Average£681FlexibilityNo cancel feeOn-time78%
Search Austrian Airlines flights
Vietnam AirlinesCheapest£611Average£807FlexibilityNo cancel feeOn-time81%
Search Vietnam Airlines flights
Singapore AirlinesCheapest£658Average£775FlexibilityNo cancel feeOn-time81%
Search Singapore Airlines flights
Thai AirwaysCheapest£881Average£1,012FlexibilityNo cancel feeOn-time77%
Search Thai Airways flights

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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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