By Air: There are small airports in Phitsanulok and Sukhothai. There are several flights a day to and from Bangkok, and less frequent flights to and from Chiang Mai. Thai Airways services both airports; Bangkok Airways, which actually owns the Sukhothai airport, does not fly to Phitsanulok. There is no commercial air service to Tak Province.
By Bus: Buses run between Bangkok's Mo Chit Northern Bus Terminal to every major town in the region. Buses also run between Phitsanulok and Sukhothai and from Tak to Sukhothai and Phitsanulok.
By Car: The main road in the region is Highway 1, which runs from Bangkok to Chiang Rai. After traveling north on Highway 1, you'll take Highways 32 to Ayutthaya, Highway 101 to Sukhothai, and Highway 117 to Phitsunalok; you can follow Higway 1 all the way to Tak Province.
By Train: The rail system is rapidly aging, with antiquated trains sluggishly making trips between Ayutthaya, Sukhothai, Kanchanaburi, Lopburi, and Phitsunalok. Trains depart for these destinations 11 times per day between 7 AM and 10 PM.
By Tuk-Tuk & Songthaew: Songthaews travel between towns in central Thailand, but are not usually as efficient or comfortable as taking the bus. Once you're in town, tuk-tuks are a convenient way to get around.