Wat Ton Chan is a temple ruin south of Sukhothai's old city, close to Wat Kon Laeng. Its remains include a broad assembly hall and a large brick chedi, surrounded by the traces of an old moat.
The most memorable detail is the broken seated Buddha in the assembly hall, now reduced to a torso and legs. It is a secondary stop, but a worthwhile one if you are exploring the quieter ruins beyond the main historical park circuit.