AirHint found the following cheapest return flights from Seattle (SEA) to Bangkok (BKK) in December 2025 (see full year).

Return flights

02 Dec - 24 Dec	Korean Air
02 Dec - 17 Dec	Korean Air
02 Dec - 15 Dec	Korean Air
02 Dec - 16 Dec	Korean Air
04 Dec - 10 Dec	Korean Air
09 Dec - 21 Dec	Hainan Airlines
08 Dec - 15 Dec	Hawaiian Airlines
10 Dec - 21 Dec	Hawaiian Airlines
04 Dec - 09 Dec	ANA
14 Dec - 14 Jan	Frontier Airlines
14 Dec - 21 Dec	Hawaiian Airlines
25 Dec - 08 Jan	Air Canada
15 Dec - 08 Jan	Cathay Pacific
07 Dec - 01 Jan	Asiana Airlines
25 Dec - 05 Jan	Korean Air
27 Dec - 01 Jan	STARLUX Airlines
24 Dec - 01 Jan	Korean Air
22 Dec - 05 Jan	Alaska Airlines
26 Dec - 04 Jan	Hawaiian Airlines
23 Dec - 03 Jan	Korean Air

Also check the deals for one-way flights from Seattle to Bangkok in December.

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 Seattle to Bangkok in December from $677

Return flights