Something of a minor transport hub Phrao actually boasts no less than four roads—one in each direction—so you’ll find songthaews heading east over the mountains to Wiang Pa Pao, west to Chiang Dao (both on the 1150) and both songthaews and minibuses departing on the southerly route for Chiang Mai via Mae Taeng.
There may also be occasional pick-ups heading north on the 1346 towards Chai Prakarn but these seem a bit sketchy, so for all points north it’d be safer changing in Chiang Dao. (It is a great ride or drive if you have your own transport though.)
Transport for Chiang Mai’s Chang Puak bus station departs every 30 minutes throughout the day between the hours of 05:30 and 17:30. Of these the 06:30, 07:30, 11:00, 12:30 and 16:30 ones are minibuses—the rest songthaews. Minibuses cost 80 baht taking around 90 minutes and songthaews 60 baht for approximately two hours travelling time.
There are also 2 or 3 songthaew departures per day for Chiang Mai taking the Chiang Dao route; at 06:10, 12:00 (possibly) and 15:30. Alighting in Chiang Dao will cost you 30 baht.
Wiang Pa Pao songthaews depart at 10:00 and 12:00 taking around 1.30 minutes and also costing 60 baht. Once at Wiang Pa Pao you’re on the main Highway 118 where you can wait around for connections north to Chiang Rai or south to Phayao or Chiang Mai.
Finally, buses to Chiang Dao run at 06:00, 12:00 and 15:30 and cost 30 baht.
For Bangkok services you’ll need to head either to Chiang Dao or Chiang Mai.
Note rural songthaew services aren’t exactly fixed in stone so the above schedules—checked in early 2018—are intended as an approximate guide only and for the less frequent services in particular you’ll need to check just prior to your date of travel.
Phrao’s small bus station is located just down the road that runs north at the side of Wat Kang Wiang.
Phrao Bus Station T: (082) 895 1350