If flying regionally from Asia to Bangkok, summer incl August can be a good deal. But TransPac, avoid August, very busy season with students and families going back and forth in both directions, and prices are high. Get into September and you should see better fares, October also usually good and sometimes the first part of November. March-May also not bad (except for Songkran mid-April period).

It doesn't get much worse for fares than mid-December to early January.

You may find that taking a domestic USA positioning flight to a major gateway city and then flying from there works better. A NYC-based friend swears that the best way to get to Asia is on Emirates via Dubai, she seems to routinely get $800 round-trips to East/SE Asia except in the Christmas season. If you can find something on Delta to anywhere in SE Asia (may have to go via NRT connection) where that credit would be honored, it would be a good way to use it.