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

Return flights

23 Sep - 27 Sep	Thai VietJet Air
21 Sep - 28 Sep	Jeju Air
18 Sep - 25 Sep	Jeju Air
19 Sep - 26 Sep	Thai VietJet Air
25 Sep - 28 Sep	Jeju Air
20 Sep - 27 Sep	T'way Air
22 Sep - 29 Sep	HK Express
27 Sep - 04 Oct	T'way Air
22 Sep - 26 Sep	T'way Air
28 Sep - 05 Oct	T'way Air
29 Sep - 06 Oct	Jeju Air
26 Sep - 03 Oct	HK Express
24 Sep - 01 Oct	Jin Air
25 Sep - 02 Oct	T'way Air
29 Sep - 01 Oct	Jin Air
23 Sep - 30 Sep	T'way Air
28 Sep - 01 Oct	Jin Air
30 Sep - 07 Oct	T'way Air
24 Sep - 30 Sep	Cathay Pacific
30 Sep - 03 Oct	Air China

Also check the deals for one-way flights from Bangkok to Ulaanbaatar 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 Ulaanbaatar in September from 351€

Return flights