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Cheap flights from London Heathrow Airport to Siem Reap from £327

LHR — SAI
10 Oct — 17 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 14/1219:25 -
2 stops19h 55m
Deal found 5/9£607
Wed 9/921:20 -
3 stops40h 50m
Wed 7/1021:10 -
2 stops27h 30m
Deal found 5/9£636
Wed 16/921:20 -
3 stops40h 50m
Wed 14/1021:10 -
2 stops27h 30m
Deal found 9/9£637
Tue 10/1111:30 -
2 stops39h 25m
Thu 3/1209:55 -
2 stops29h 10m
Deal found 5/9£640
Wed 30/906:00 -
2 stops30h 55m
Wed 28/1009:55 -
2 stops29h 10m
Deal found 7/9£644
Tue 10/1108:30 -
2 stops42h 25m
Sat 5/1216:50 -
2 stops24h 55m
Deal found 6/9£657
Wed 21/1017:30 -
2 stops34h 10m
Wed 28/1019:25 -
2 stops19h 40m
Deal found 6/9£662

Find flight deals from Heathrow to Siem Reap

Round-trip from

£607

One-way from

£327

Popular in

December

Cheapest in

July

Average price

£765
Austrian Airlines
  • Austrian Airlines
  • 3/12-14/12
  • 4 total stops
  • 49h 25m total
  • London to Siem Reap
Search Deals
21/9-31/12
  • 21/9-31/12
  • 2 total stops
  • 37h 55m total
  • London to Siem Reap
Search Deals
Highest demand for flights based on searches. 10% potential increase in price (£67 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 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

Mon 21/9

22:10-18:05

2 stops37h 55m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£327

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Tue 1/12

10:45-18:05

3 stops48h 20m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£359

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Fri 26/2

07:05-16:05

2 stops26h 00m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£372

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Wed 4/11

06:00-15:00

3 stops26h 00m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£401

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

£420

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Mon 4/1

06:50-09:20

3 stops43h 30m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£425

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Sat 14/11

19:25-18:30

2 stops40h 05m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£444

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Fri 1/1

17:45-17:25

3 stops40h 40m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£451
Fastest return journey

LondonSiem Reap

LHR London Heathrow - SAI Siem Reap–Angkor Intl

LHRSAI

London Heathrow

Tue 2/2

09:55-16:05

3 stops23h 10m

Siem Reap–Angkor Intl

Wed 31/12

00:00-18:00

Nonstop0h 00m

£495

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

17:55-07:15

1 stop20h 20m

£770

Flights are sorted by cheapest return flights first.

Deals found on 8/9

Showing 1-10 of 15 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 £683). Flying from London Heathrow Airport to Region of Siem Reap in July is currently the most expensive (average of £903). 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
1,599 reviews
Check prices

Crew

8.6

Entertainment

8.1

Comfort

8.0

Boarding

8.3

Overall

8.2

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
1,599 reviews
Singapore Airlines
8.2
Very Good
1,599 reviews
Check prices

Crew

8.6

Entertainment

8.1

Comfort

8.0

Boarding

8.3

Overall

8.2

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
418 reviews
Singapore Airlines
8.2
Very Good
1,599 reviews
Check prices

Crew

8.6

Entertainment

8.1

Comfort

8.0

Boarding

8.3

Overall

8.2

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
1,599 reviews
Check prices

Crew

8.6

Entertainment

8.1

Comfort

8.0

Boarding

8.3

Overall

8.2

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
958 reviews
Singapore Airlines
8.2
Very Good
1,599 reviews
Check prices

Crew

8.6

Entertainment

8.1

Comfort

8.0

Boarding

8.3

Overall

8.2

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 26h 30m. Vietnam Airlines provides one of the quickest options available for as low as £770. 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?

    £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 £448 and £500, 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 £683). Flying from London Heathrow Airport to Region of Siem Reap in July is currently the most expensive (average of £903). 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£535Average£682FlexibilityNo cancel feeOn-time78%
Search Austrian Airlines flights
Vietnam AirlinesCheapest£611Average£808FlexibilityNo cancel feeOn-time81%
Search Vietnam Airlines flights
Singapore AirlinesCheapest£658Average£788FlexibilityNo cancel feeOn-time81%
Search Singapore Airlines flights
Thai AirwaysCheapest£882Average£1,013FlexibilityNo 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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