TPAC fares from the US are extremely high, with flight volume still nowhere near pre-covid levels. I assume the lack of through flights on Chinese carriers is a primary reason.

I will add, somewhat OT, that Bangkok seems more crowded than I've ever seen it (mostly with Thais), MRT was insane today. Traffic was insane. Very very different from the US, where many big city downtowns have not come close to returning to pre-covid activity levels.