Both the WAT mahathat in Sukhothai and Ayutthaya WAT mahathat at UNESCO World Heritage site, the ancient ruins are marvelous. But the location makes day trip to Ayutthaya if you are in Bangkok.
Wat Mahathat and Wat Mahathat at Sukhothai and Ayutthaya, a World Heritage Site by UNESCO, a great ancient ruins. But the location of Ayutthaya, making travel convenient day if you are in Bangkok.