The fastest way in is to fly. Bangkok Airways has daily flights from Bangkok Suvarnabhumi to Sukhothai's small private airport, 27 km northeast of the new town; the airline runs a shuttle bus from the airport to either the new town or the historical park.
By bus, Sukhothai is on the main route from Bangkok's Mochit terminal (about 7 hours), and is connected to Chiang Mai (5 hours), Phitsanulok (1 hour) and Ayutthaya. By train, the nearest station is Phitsanulok on the main Bangkok–Chiang Mai line; a frequent minibus shuttles between Phitsanulok station and Sukhothai (about 1 hour).
Inside Sukhothai, the new town and the historical park are 12 km apart, linked by a frequent songthaew during the day (about 30 baht) and many tuk-tuks and motorbike rentals.