After taking the 3,5h bus from Chiang Rai to Chiang Mai in the morning, I felt very tired and looked with dread toward the overnight train, where I booked a 3rd class 7$ seat, because the sleeping cabins were sold out. But it turned out: it wasn‘t that bad, except that I smell like metal now. I met some great people on the way, the view and sunset were stunning and I got a good portion of sleep. Can‘t ask for more for 7$.