United Airlines has Los Angeles to Bangkok at $518 round trip flying ANA operated flights via Tokyo. Departure dates for these low fares are from September into December. Layover time is relatively short in Tokyo at under 2 hours for either Haneda HND or Narita NRT, but midday departure times are a bonus.
And even better than discount Basic Economy fares to Europe where a checked bag is a high fee addition, these cheap flights to Asia include free checked bag.
United Airlines Los Angeles LAX – Tokyo NRT – Bangkok BKK – Tokyo HND – LAX