AirHint found the following cheapest return flights from Chiang Mai (CNX) to London (LHR) in September 2025 (see full year).

Return flights

02 Sep - 05 Oct	Thai VietJet Air
03 Sep - 17 Sep	China Eastern
05 Sep - 12 Sep	Thai VietJet Air
15 Sep - 27 Sep	EVA Air
03 Sep - 14 Sep	Cathay Pacific
11 Sep - 16 Sep	Cathay Pacific
03 Sep - 29 Sep	Cathay Pacific

Also check the deals for one-way flights from Chiang Mai to London in September.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Chiang Mai to London in September from $915

Return flights