Korean Air has round-trip flights from Dallas (DFW) to Chiang Mai (CNX) for $727-$788 with a connection. Flights in November and March. Departures on Tuesday, Wednesday, and Thursday. 7-day minimum stay required. No Thanksgiving dates.
Some small OTAs on Skyscanner have this for as low as $727; which is cheaper than the airline. If you plan on booking there, beware of any site that charges a fee to cancel a ticket within the 24-hour “free” period. Use unknown booking sites at your own risk.