To go to Si Satchanalai ?
Si Satchanalai is located sixty kilometers from Sukhothai.
Some buses from Bangkok (Mochit Bus Terminal) to Chiang Mai go to Si Satchanalai Historiccal Park, you can take them directly from Bangkok or from Sukhothai Bus Terminal. Bus number 100 also goes from Bangkok to Si Stachanalai and stop by at Kampheng Phet.
If you are in Sukhothai, there are some Wintour buses that you can take at New Sukhothai bus terminal and will pass not far from Si Satchanalai Historical Park. They can drop you on the main road just before a street leading to Wat Phra Si Rattana Mahathat. There you will see a small grocery store where the owner also rents bicycles (50 THB per day). Leave early in the morning to have the time to visit the park and catch the last bus to go back to Sukhothai. Otherwise, there are some guesthouses between Si Satchanalai Historical Park and Wat Phra Si Rattana Mahathat temple but if you go in the morning, it is just a one day trip from Sukhothai. You can find the timetable forbuses from Sukhothai to Si Satchanalai