Don’t bring jeans or clothes made of 100% cotton
Thais wear jeans, but it’s safe to say that most Westerners aren’t acclimated to the heat and will be waaay too hot. Jeans also take a long time to dry on a clothesline and are heavy in your suitcase. (Thick) 100% cotton shirts also take a long time to dry and wrinkle easily and don’t always keep you cool. Leather (faux or real) will give you rashes in places you don’t want.