I don't know what the problem is with Thailand but they sure are "illogically" violent against foreigners. This is going to be another big blow to tourism over there.
It looks like some altercation was happening there before they arrived on the scene and it looks as though they walked into it. You also can see the mother clearly get "powerfully" kicked in the face.
Very brutal and especially sad.....
British family beaten unconscious by gang in thailand tourist resort | Daily Mail Online