Makes some  nervous as they cannot see your eyes to gauge you and guess upto how much they can cheat you. 

22 hours ago, bendejo said:

Sunglasses are distancing, I usually take mine off (and replace them with clear-lensed glasses) when I enter a shop or mall.  Anyone venturing into Latin America should bear this in mind.

 

The man with no eyes from Cool Hand Luke.

 

Finally, someone who understands...

 

Distancing" is the correct term. They create a distance and boundry many Thai's are not comfortable with. People who want to engage everyone to be comfortable don't like sunglasses.

 

You were not to eyeball or address the boss man directly. The sunglasses symbolized this. I don't get many people eyeballin' when I wear mine.

Another proponent of using sunglasses to give people the creeps was Haiti's Tonton Macoute.