Self-selection.
The positive happy-going guys too busy getting out there, enjoying Thailand and having a blast. Hence, no time to obsessively post on forums.
But the grumpy guys have nowhere else to go but to become keyboard warriors, because it's not cool to be a grumpy sour-faced guy in the Land of Smiles, where looking angry is impolite and looked down upon.
Life ain't perfect. The glass is always either half full or half empty depending on how you look at things.
Just enjoy what you have and you will be happy wherever you are.
Just my 2 cents.