Wat Khun Muang Chai is a large temple ruin located on the city island. It can be easily found on the northern side of Rochana Road, just before the intersection with Chikun Road. The Fine Arts Department restored this monastery in 1969-1970 and once again in 2006.
Wat Khun Muang Chai was once located beside Khlong Pratu Khao Pluak, but this canal has since been buried. It is most likely featured on several maps by foreigners, including Vingboons 1660 map and de La Mare 1751 map (though in the latter it is slightly misplaced). This monastery also appears on Phraya Boran Rachathanin’s 1926 map. Interestingly, Phraya Boran Rachathanin draws it at on northwest/southeast axis. This seems odd because Wat Khun Muang Chai clearly runs from east to west, and it perfectly parallels Rochana Road.
Wat Khun Muang Chai consists of four primary structures: an ubosot, one wiharn, a large stupa, and a two-story living quarters. Of these structures, the large stupa is probably the most breathtaking. The tall base of the stupa consists of several layers that support a bell-shaped body as a type of relic chamber. One layer is superimposed over another. This style of Thai architecture is known as “Yok Ket”. On the southeastern side, a surviving corner chedi is still visible. There are very few monasteries resembling Wat Khun Muang Chai in Ayutthaya (Wat Ayodaya being one of them). This chedi has low walls above its indented base that are designed to look like balustrade walls. These still have some decorative stucco patterns intact - including a few niches where a standing Buddha image can still be seen. These patterns and Buddha images reflect a Khmer influence, and there is evidence that several restorations were done on the chedi during ancient times (TAT 114-115).
There are sermon halls on both sides of the central chedi. These have been restored by the Fine Arts Department as well. The sermon hall on the western side is very elaborate. Its foundation is in good shape and a large number of chedi are in situ. One of these smaller chedi (with a hollow entrance) is at an angle so steep that it appears to be falling over. The sermon hall on the eastern side is much smaller and more damaged. Nevertheless, this structure includes some remnants of Buddha images and a reasonable preserved foundation layer. A large bodhi tree grows out of its altar. A two-story building is located on the northwestern side of Wat Khun Muang Chai. This type of structure is associated with residential halls of highly positioned monks or members of the royal family. There are ones like it at Wat Kudi Dao and Wat Chao Ya.
Wat Khun Muang Chai is a very ancient temple. It may pre-date the establishment of Ayutthaya in 1351. In fact, this monastery is often connected with Ayodaya - an earlier settlement east of the city that had a connection to the Lopburi empire. “Archaeologists have found traces of a pre-12th century Dvaravati town on and below the island of Wat Khun Muang Chai, Wat Maha That, and Tambon Bang Kracha (Garnier 39-40). This claim is backed up by a map hanging on the walls of the Ayutthaya Historic Study Center. The map suggests that there were also a collection of Brahmin shrines north of Wat Khun Muang Chai. The collection of multiple religious sites within the same alignment implies that Khlong Pratu Khao Pluak was the boundary of the former Ayodaya settlement. This belief is supported by a number of historians. “When the city was founded in the reign of King U-Thong, the eastern perimeter probably stretched only to Pratu Khao Phluak or Pratu Chin canal, situated in the middle of the island” (Kasetsiri & Wright 320).
Even though Wat Khun Muang Chai is quite ancient, there are not many records of its history. Documents refer to it being used for the important ceremony of taking oaths of allegiance (TAT 114-115). Royal Chronicles mention a Khun Muang who was a noble during the reign of King Borommatrailokanat, who ruled Ayutthaya from 1448-1463 before ruling in Phitsanulok for twenty years (Cushman 15). A second Khun Muang is referred to during the reign of King Narai. This man was appointed to the right wing of the Royal army sent to Sukhothai. An oath of allegiance was taken around that time (Cushman 253). However, it is uncertain if these passages have any connection to the monastery.