Thing is It's not clear whether this is an overbooking issue, a fraud check issue, or both. If it were simply overbooking then it should have been pretty easy to get rebooked at the airport. With the fraud questions it sounds like QR don't really want to do anything with it at all.

There is of course another option which might be easiest if OP is confident that a refund is definitely being issued - simply buy brand new tickets on whichever airline is cheapest/most convenient out of BKK today. There are many servicing that route.