Loss of Face
Cambodians are always smiling. In Cambodia, a smile is never far away, and Khmers are known around the world for their trademark grins. This quality, which is sometimes accompanied by a twinkle in the eye, helps first-time visitors feel at rest from the moment they step foot in the country, while returns feel at ease.
This does not always imply that they are happy or that they comprehend when they nod and grin in agreement, which can be frustrating. In Cambodia, losing face, which includes admitting you don't know anything, is a serious problem.
It's preferable to ask again if the smile is followed by a frightened chuckle. So, if the waitress grins, appears little perplexed, and laughs when you order your food without extra chilli, double-check your order.