AirHint found the following cheapest return flights from Seoul (GMP) to Bangkok (BKK) in September 2025 (see full year).

Return flights

24 Sep - 16 Oct	Jeju Air
24 Sep - 21 Oct	Jeju Air
24 Sep - 15 Oct	Jeju Air
25 Sep - 02 Oct	Eastar Jet
29 Sep - 01 Oct	Jeju Air
24 Sep - 25 Sep	Jeju Air
27 Sep - 16 Oct	Jeju Air
24 Sep - 03 Oct	Jeju Air
24 Sep - 04 Oct	Jeju Air
27 Sep - 29 Sep	Jeju Air
23 Sep - 15 Oct	Jeju Air
24 Sep - 05 Oct	Jeju Air
23 Sep - 27 Sep	Eastar Jet
24 Sep - 26 Sep	Jeju Air
23 Sep - 29 Sep	Jeju Air
23 Sep - 25 Sep	Jeju Air
27 Sep - 28 Sep	Jeju Air
26 Sep - 28 Sep	Jeju Air
23 Sep - 26 Sep	Jeju Air
22 Sep - 29 Sep	Air China

Also check the deals for one-way flights from Seoul to Bangkok 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 Seoul to Bangkok in September from 180€

Return flights