United Airlines with codeshare partner ANA have roundtrip airfares travelling from Houston (IAH) to Bangkok Thailand (BKK) for $635 including taxes and fees. This makes 1 stop in Tokyo Japan. Flights are operated on ANA
Departs IAH: Every Mon/Tue/Wed/Thurs beginning on Aug 20 thru Oct 31, 2018
Returns: wide and good availability
Use dates and book it on Orbitz [orbitz.com]
or Priceline [priceline.com]
or United Airlines [united.com]
directly. Bundling hotel with airfare will save money.
Sample travel itinerary attached.