I'd expect there to be regular buses through the day between Udon and Phitsanulok. I'm guessing here, but probably somewhere between 100 and 200B and 4-6 hours. It's a pretty trip.
I've been on this route in a car it goes thru a couple national parks, pretty scenary maybe more than 6 hours thou in a bus, callao
#4 callao has been a member since 4/8/2007. Posts: 5