Korean Air has round-trip flights from New York (JFK) to Bangkok or Chiang Mai (BKK, CNX) for $738 with a connection. Flights in November. Departures on Monday and Tuesday. 7-day minimum stay required. No Thanksgiving dates.
Some small OTAs on Skyscanner have this for as low as $699; 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.
A Carry-on bag and also a personal item is allowed for free. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.
Click for more details and booking links Cheap Flights: New York to Bangkok or Chiang Mai $699-$738 r/t [November] (No Thanksgiving) – Korean Air / Asiana Airlines