The historical park is best explored by bicycle. Several shops just outside the eastern (main) gate rent decent bikes for about 30 baht a day. The central zone is flat and shaded and a bicycle is genuinely the best way to do it; the outer zones (north, west, south) are accessible by bike too if you have the legs, though many visitors switch to a motorbike (around 200–300 baht a day from the new town) for the more distant ruins and for Si Satchanalai.
Tuk-tuks ply the road between the new town and the park (around 80 baht per person) and can be hired for the day at the park gate.