The first thing you notice arriving in Cambodia after spending times in Thailand is the absence of open smiles on people's faces. When you cross your sight with a passerby in Bangkok, when you ask for information to somebody that doesn't even speak English, what you get is that, a smile. Even during the red shirts revolution on the barricades you would mostly notice smiles (until the shootout started, of course). In Phnom Penh the mood is different. Culture is certainly different, the character is different, but what is really different, is my opinion, is the recent history of these countries. Thailand has not known the war for centuries now: it was untouched in the 2nd WW and it was an heaven during the Vietnam war. Cambodia, viceversa, is still recovering from the deepest darkness, social and human darkness, we can imagine: decades of war, civil repression, massacres, poverty. Even worse then Vietnam, in many ways. Today it's economy is slowly growing, but under the heavy hand of China that is not paying much attention to social differences here.
I visited the Tuol Sleng today, the Genocide Museum that was the slaughterhouse under the Khmer Rouge regime. A long gallery of cells, torture chambers, and thousands of pictures of people that died here. And then you understand why people are not smiling, at least not yet. It will take generations for wounds to heal, for Cambodians to look at others seeing friendly visitors, or at least not indifferent foreigners. The world was silent, for too long.