Indeed, it must be a joke! BA was offering fares to BKK for £850 until a couple of days ago. It was a companion fare, but that clearly applies here. QF also great deals. TG is now offering around £1500. Even SQ was beating CX handily ex-LHR.
What was your fare on CX? Or maybe you need to stop in HKG. But even so, the BA fare was much better adding a BKK-HKG leg.