Located in Northern Thailand, Pai is a small town in the countryside. It's only a 3-4 hour ride from Chiang Mai, but it's quite a nauseating one. There are 762 turns along the way, so make sure to take some anti-nausea medication beforehand.
Mini-Bus
We booked a mini-bus from our hostel for 200 baht each. You can also book a mini-bus at the station, however they cost 150 baht and it's also another 40 baht red truck ride to get to Arcade Bus Station. So, it's about 190 total if you do it on your own. They leave hourly and it takes about 3 hours to get to Pai. You'll get a short break halfway through to use the washroom (3 baht) or grab some grub.
Public Transit
If you have a really strict budget, you can take public transit to get there. You can book a bus ticket for 78 baht + the 40 baht red truck ride to the station. Although these buses don't offer AC. The bus leaves at 7 a.m. and it takes 4 hours to get there.
Other options
If you're feeling luxurious, you can book a flight to get to Pai.
If you're feeling adventurous, you can ride a motorbike there, although I wouldn't recommend it unless you are a skilled rider. The curves make it a very dangerous trip. We saw someone fall after a curve.