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

Return flights

29 Sep - 06 Oct	Korean Air
23 Sep - 22 Oct	Korean Air
16 Sep - 06 Oct	Korean Air
25 Sep - 30 Sep	Cathay Pacific
24 Sep - 01 Oct	Cathay Pacific
29 Sep - 15 Oct	Korean Air
17 Sep - 23 Sep	Cathay Pacific
15 Sep - 22 Sep	Cathay Pacific
17 Sep - 24 Sep	Cathay Pacific
16 Sep - 01 Oct	Cathay Pacific
18 Sep - 25 Sep	Delta
29 Sep - 14 Oct	Cathay Pacific
21 Sep - 30 Sep	Cathay Pacific
28 Sep - 12 Oct	Cathay Pacific
22 Sep - 04 Oct	Cathay Pacific
26 Sep - 29 Sep	Cathay Pacific
25 Sep - 28 Sep	Delta
15 Sep - 28 Sep	Delta
27 Sep - 02 Oct	Cathay Pacific
21 Sep - 28 Sep	Delta

Also check the deals for one-way flights from Chicago 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 Chicago to Bangkok in September from $664

Return flights