I don't know if someone else has already reported this. If they have, sorry it must have slipped by my radar.
When I first started coming to Thailand the direct flight choice from London used to be limited to 3 carriers.
Then, a little while ago from memory, BA opted out of their partnership deal & the 3rd, choice became Quantas only.
I now read that Quantas are finishing the Bangkok to London route in March this year.http://www.bbc.co.uk/news/business-17053703
They have also just cut a few other long haul routes because of falling half year profits, but the London decision was made prior to that anyway.
I only took the flight once with them & was disappointed enough not to want to repeat the experience, but I am sorry that they are finishing as more choice is always better than less.