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

Return flights

17 Sep - 24 Sep	Thai AirAsia
20 Sep - 11 Oct	Thai AirAsia
08 Sep - 11 Sep	Thai AirAsia
09 Sep - 27 Sep	Thai AirAsia
22 Sep - 29 Sep	AirAsia
09 Sep - 16 Sep	Thai AirAsia
09 Sep - 30 Sep	Thai AirAsia
27 Sep - 02 Oct	Thai AirAsia
14 Sep - 23 Oct	Nok Air
25 Sep - 15 Oct	Thai AirAsia
23 Sep - 11 Oct	AirAsia
15 Sep - 22 Sep	Nok Air
18 Sep - 26 Sep	AirAsia
18 Sep - 25 Sep	Nok Air
09 Sep - 26 Sep	AirAsia
26 Sep - 04 Oct	Thai Lion Air
30 Sep - 15 Oct	Nok Air

Also check the deals for one-way flights from Bangkok 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 Bangkok to London in September from 603€

Return flights