UA/NH: IAD-BKK, $650 limited dates Jul/Aug/Sept
WAS-BKK, UA/NH through Tokyo, $650 or so. Can price on google flights, but to actually book must enter specific flights on United site in multi-destination mode and specify K booking class.
Available Mon-Wed (depart and return) starting July 23rd, sample dates July 23-Aug 22 and each week thereafter.