Update: picked the $19 night bus from Bangkok to Chiang Mai over the $70 flight and I'm still recovering
Traded 12 hours of my trip for $51 in savings and ended up wedged next to a guy who snored the entire ride, so next time I want to know if anyone has actually made that haul work without wanting to die by hour 8?
12 hours is rough but the flight is only about an hour and ten minutes, so you didn't really trade 12 hours for $51. You traded maybe 10 or 11 at most once you count getting to the airport, security, and the ride from CNX into town. I did the sleeper train once for around 700 baht and it was fine because you get an actual bed, but the buses are a different thing. A reclining seat for that long with someone snoring in your ear is never going to work. If you want to save money on that route, the train is the move, not the bus.