That's interesting; because I don't know that TG has a mechanism for being compensated for an xONEx ticket, which are typically (or at least used to be -- I haven't done an AONEx for several years, though I start one in mid-November) validated as valid on OW carriers only. Theoretically it shouldn't invalidate the remainder of your ticket because CX knows about it and CX is the carrier who operates the flight on which you will "noshow" -- however, I emphasize theoretically. It can't hurt to call and ask. And get the name of the agent with whom you speak. Potentially avoids huge probs later if I'm wrong.

Unless you're already at the airport, go early enough (I'd say an extra 1-2 hours) to enjoy and experience the TG F lounge and service. IMO TG F is one of the best in the world on the ground at BKK, not so much in the air, though.