If it somehow turned out that this couple was indeed hacked down by a fellow countryman, Thaivisa is going to go into a total meltdown; but how can it be ruled out at this stage?

If they had all been staying at the same place, drinking, partying and who knows what, it's a possibility that something went sour between them.

Farangs do kill each other from time to time....and not infrequently over a good looking girl... It's not always a Burmese gardener or a an angry somchai....