I personally would go CX (despite the current issues in HK) as they will offer you the most direct route there is on OW.
As someone else mentioned, if TP optimisation is a factor, then MH will likely workout as not only the cheapest regardless, but also best on TP earnings (same as JL, but they will be more expensive).
Hope you will have a good time in my adopted home country! Be conscious that Christmas time is peak tourist season though, and China is a big source market for Thailand - you should look into booking sooner rather than later
That said, TG direct would probably be the best option although obviously not OW