The Phra Borommathat Chedi, locally known as "Phra Borommathat Tan Jai," is the principal stupa located behind the main viharn of Wat Phra Chao Tan Jai. The stupa is designed in the Lanna-style bell shape, with a high stepped base covered in intricately carved brass sheets (Thong Jangko). It enshrines Holy Relics of the Buddha (some legends mention hair and bone relics). This monument stands as the spiritual heart of the Ban Ton Thong Chai community. It is traditionally linked with the "Phra Chao Tan Jai" Buddha image, as devotees believe that paying respects to both the stupa and the image will bring swift success and the fulfillment of their wishes.