[RagonaCon]

Most private cars in Thailand have tinted windows. Mine does and I can't drive with sunglasses on otherwise I can't see a thing.

This and also most Thai who're so scare of the sun will be spending time in air-cooling shopping malls most of the time if they choose to go "outdoor". So I don't see the need for sun glasses. I think its still fairly common to spot young people wearing sun glasses in trendy venues like Siam Square and Paragon though.