Sorry but "Loss of Face" is not an acceptable reason to kill someone over, Especially for some of the reasons you have mentioned above...
That guy from the UK was doing what any guy would do when that so-called policeman was trying to proporsition his girlfriend and start offering him money to sleep with her and would not back off when asked too and then became aggressive, Nearly any guy from any country in the world would do the same, And not expect to be killed for it, And can you tell me why he chased after the girl, Ran her over, Turned around and shot her twice just for good measure?
What "Loss of Face" because she refused to sleep with him for money, And rejected his advances?
Another thing, Thats a nice little spin you put on how the Thai's act while being paraded in front of the camera's after the crime, I could be also be seen a them not giving a fu*k about what they have just done because life does not hold much value to them, It can be seen as a total lack of respect for the victim and that they show absolutly no remorse for it, Which is a very dangerous thing.
And you mentioned the killing of over 2,000 people in the war on drugs, Again that just shows how little life is valued to them, And a farangs life would be even less valueble, Now thats scary.
The thing that gets to me is people trying to cover over the cracks and make Los out to be the safest place in the world, Thats just not true, Its only safe if you are aware of what to look out for and aware of whats going on around you an what to avoid, Its by trying to cover the bad things about that place which makes it worse.