I am surprised by your experience re fares.
I am a regular flyer on this route (BKK/LHR), averaging something like 1 round trip every 6 weeks and, from my experience, TG (F/P) is pretty much always more expensive than the other options, though , obviously, it does offer the benefit of the direct flight.

I have found EK to be (in general) considerably cheaper than TG , but i am not a fan of the timings and the break in the desert. I have also had good fares on a combination of LH/LX ie LH ex BKK and return on LX. I am now a fan of both airlines.

I have gradually been running down any awards/miles that i have left on TG (not an easy exercise) and increasingly switching my full fare travel to LH/LX.
TG have "punished" me for this by taking away my Platinum status.

I have also experienced the blanket over the TV (solution) on several Thai flights in the past - hilarious!