They all smile
One of the best things about Thailand and the reason it gets the nickname “The Land of Smiles” is the very outgoing and social nature of the Thai people. After a while you will notice this and say to yourself, “They really do all smile.
One thing I have noticed about Thai culture is they really do not put a lot of stress on themselves individually. There is PLENTY of time for things that are uplifting, be it coffee with friends where you will see groups out at any hour of the day sitting among a group socializing, or to the many festivals they have. It seems like there was a different festival for something different every weekend of the many trips I had there. Water festivals, car shows, beach sport festivals, music festivals, they seem to pop up everywhere and some of the night markets even have that festival feeling. All of this is very uplifting and keeps the local people in good spirits.
If you greet someone in Thai, you are generally met with a great smile before they return the gesture.