Wat Rong Tham was a monastery situated off the city island in the eastern area of Ayutthaya in present Phai Ling sub-district.
The monastery stood (likely) south of Wat Pradu on the south bank of the today defunct Khlong Wat Pradu. The premises of Wat Rong Tham and Wat Pradu were merged to become Wat Pradu Rong Tham, presently known as Wat Pradu Songtham. (1)
Its historical background and period of construction are unknown.
The site is indicated on Phraya Boran Rachathanin's [PBR] map drafted in 1926. PBR indicates Khlong Pradu south of Wat Rong Tham, but this might be incorrect and possibly be another canal. Kaempfer positions Khlong Pradu north of Wat Nang Chi and above the mouth of Khlong Pratu Ho Ratanachai on the opposite side on his map drafted in 1690, hence Wat Rong Tham and Wat Pradu were separated by the canal.
Wat Rong Tham was located approximately in Geo Coord: 14° 21' 48.61" N, 100° 35' 14.79" E.
(1) The renaming of "Rong" by "Song" seems to come from the following: "rong" which means building, sounds also as coffin (Th: long). The word "rong" was not felt as a very auspicious name for a temple, hence the name change. The same occurred to Wat Wong Khong, before known as Wat Rong Khong and later changed into Wat Wong Khong. Other Ayutthayan temples which were merged at a certain stage are Wat Sri Pho (Wat Sri Pho & Wat Phrom Kalayaram) and Wat Tha Ka Rong (Wat Tha & Wat Ka Rong).
(Extract of Phraya Boran Rachathanin's map - Anno 1926)