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Cheap flights from London Heathrow Airport to Siem Reap from £358

LHR — SAI
20 Oct — 27 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

Thu 3/1206:00 -
2 stops29h 30m
Mon 14/1209:55 -
2 stops18h 45m
Deal found 16/9£631
Wed 23/922:10 -
2 stops37h 55m
Wed 30/919:10 -
1 stop27h 45m
Deal found 15/9£676
Fri 6/1119:25 -
2 stops16h 05m
Fri 20/1116:50 -
2 stops27h 00m
Deal found 15/9£681
Thu 24/906:40 -
2 stops24h 35m
Wed 7/1009:40 -
2 stops35h 40m
Deal found 18/9£687
Wed 23/906:00 -
2 stops30h 55m
Wed 21/1009:40 -
2 stops36h 45m
Deal found 18/9£688
Wed 30/922:00 -
2 stops38h 05m
Wed 28/1021:30 -
1 stop16h 45m
Deal found 18/9£690
Tue 10/1121:00 -
3 stops40h 05m
Sat 5/1221:05 -
3 stops51h 25m
Deal found 19/9£692
Wed 30/922:00 -
2 stops38h 05m
Wed 21/1019:10 -
1 stop27h 45m
Deal found 17/9£694
Sat 19/922:05 -
2 stops37h 00m
Wed 30/919:10 -
1 stop27h 45m
Deal found 15/9£698

Find flight deals from Heathrow to Siem Reap

Round-trip from

£631

One-way from

£358

Popular in

December

Cheapest in

July

Average price

£771
SWISS
  • SWISS
  • 3/12-14/12
  • 4 total stops
  • 48h 15m total
  • London to Siem Reap
Search Deals
8/12-31/12
  • 8/12-31/12
  • 2 total stops
  • 36h 35m total
  • London to Siem Reap
Search Deals
Highest demand for flights based on searches. 6% potential increase in price (£45 potential increase over avg. return price).
Search Deals
Cheapest flight prices on average. 3% potential price decrease (£23 potential savings vs. average return price).
Search Deals
Average for round-trip flights in September 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

Wed 20/1

06:50-18:05

3 stops28h 15m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£406

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Sat 13/3

19:05-16:00

3 stops37h 55m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£415

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Mon 12/10

15:50-09:35

3 stops35h 45m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£417

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Sat 28/11

19:25-18:30

2 stops40h 05m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£435
Fastest return journey

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Sat 14/11

19:25-18:30

2 stops16h 05m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£439

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Sat 28/11

18:40-18:30

2 stops40h 50m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£461

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Sat 28/11

11:00-20:30

1 stop26h 30m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£508

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Sat 28/11

11:00-18:50

1 stop24h 50m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£546

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Sat 13/3

21:45-16:00

1 stop35h 15m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£599

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Tue 10/11

20:35-16:00

1 stop36h 25m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£600

Flights are sorted by cheapest return flights first.

Deals found on 17/9

Showing 1-10 of 19 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 £691). Flying from London Heathrow Airport to Region of Siem Reap in July is currently the most expensive (average of £914). 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.

How much does it cost for a return flight from London Heathrow Airport to Region of Siem Reap?

Airfare is below average for this route at the moment.
London Heathrow Airport to Region of Siem Reap flights typically cost between £637 and £798 in December.
The cheapest return price found within the last 5 days was £631 on Multiple Airlines (3 Dec–14 Dec).

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
1,606 reviews
Check prices

Boarding

8.3

Comfort

8.0

Entertainment

8.1

Food

7.8

Overall

8.2

Crew

8.6

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
1,606 reviews
Singapore Airlines
8.2
Very Good
1,606 reviews
Check prices

Boarding

8.3

Comfort

8.0

Entertainment

8.1

Food

7.8

Overall

8.2

Crew

8.6

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
420 reviews
Singapore Airlines
8.2
Very Good
1,606 reviews
Check prices

Boarding

8.3

Comfort

8.0

Entertainment

8.1

Food

7.8

Overall

8.2

Crew

8.6

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
288 reviews
Singapore Airlines
8.2
Very Good
1,606 reviews
Check prices

Boarding

8.3

Comfort

8.0

Entertainment

8.1

Food

7.8

Overall

8.2

Crew

8.6

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
967 reviews
Singapore Airlines
8.2
Very Good
1,606 reviews
Check prices

Boarding

8.3

Comfort

8.0

Entertainment

8.1

Food

7.8

Overall

8.2

Crew

8.6

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 16h 20m. Austrian Airlines provides one of the quickest options available for as low as £637. 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?

    £380 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 £453 and £506, 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 £691). Flying from London Heathrow Airport to Region of Siem Reap in July is currently the most expensive (average of £914). 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£541Average£690FlexibilityNo cancel feeOn-time78%
Search Austrian Airlines flights
Vietnam AirlinesCheapest£618Average£818FlexibilityNo cancel feeOn-time81%
Search Vietnam Airlines flights
Singapore AirlinesCheapest£666Average£805FlexibilityNo cancel feeOn-time81%
Search Singapore Airlines flights
Thai AirwaysCheapest£892Average£1,002FlexibilityNo cancel feeOn-time77%
Search Thai Airways flights

Fly with Cheapflights

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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