Sending lanterns into the sky is actually a different festival called Lanna, just taking place on the same day. The information of where to go to see the lanterns varies highly! The internet is different to what several locals say. So there is a horrible expensive feast at a university in Chiang Mai that is made for tourists but you can watch it also from outside. The other one is right in the city pretty much everywhere. People light up lanterns mostly at the river but they were sent into the sky everywhere. So when you go to the university you miss the river where everyone puts in the Krathongs. I was happy I have been to the city in the main event. It was an awesome atmosphere, happy faces everywhere. Also stupid people not getting it that a lantern next to a tree is stupid. So take care next time if you go there!