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

Return flights

10 Sep - 25 Sep	IndiGo
09 Sep - 23 Sep	IndiGo
02 Sep - 29 Sep	IndiGo
04 Sep - 21 Sep	IndiGo
05 Sep - 17 Sep	IndiGo
09 Sep - 16 Sep	IndiGo
10 Sep - 19 Sep	IndiGo
25 Sep - 28 Sep	IndiGo
16 Sep - 25 Sep	IndiGo
10 Sep - 27 Sep	IndiGo
23 Sep - 23 Oct	Norwegian Air Sweden AOC
17 Sep - 01 Oct	Turkish Airlines
22 Sep - 29 Oct	Turkish Airlines
13 Sep - 08 Oct	Lufthansa
15 Sep - 06 Oct	Turkish Airlines
04 Sep - 01 Oct	Turkish Airlines
07 Sep - 01 Oct	Lufthansa
22 Sep - 07 Oct	Lufthansa
20 Sep - 01 Oct	Turkish Airlines
13 Sep - 11 Oct	Turkish Airlines

Also check the deals for one-way flights from Helsinki 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 Helsinki to Bangkok in September from $643

Return flights