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

Return flights

02 Dec - 15 Dec	Korean Air
02 Dec - 17 Dec	Korean Air
02 Dec - 16 Dec	Korean Air
02 Dec - 24 Dec	Korean Air
04 Dec - 10 Dec	Korean Air
05 Dec - 15 Dec	Korean Air
04 Dec - 11 Dec	ANA
06 Dec - 13 Dec	China Airlines
08 Dec - 15 Dec	Alaska Airlines
04 Dec - 09 Dec	ANA
03 Dec - 07 Jan	Asiana Airlines
25 Dec - 18 Jan	Korean Air
25 Dec - 17 Jan	Korean Air
23 Dec - 18 Jan	Korean Air
24 Dec - 18 Jan	Korean Air
30 Dec - 02 Jan	Korean Air
29 Dec - 05 Jan	China Airlines
25 Dec - 09 Jan	Korean Air
25 Dec - 08 Jan	Korean Air
23 Dec - 08 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