Engelbert Kaempfer was a medical doctor working for the Dutch VOC (Verenigde Oost-Indische Compagnie) who surveyed the city of Ayutthaya in June 1690 CE. He made a sketch during his walks in the city and afterwards drafted a map, which was not published at that time.
I compared his sketch with the later maps of Phraya Boran Rachathanin (1926 CE) and the maps of the Fine Arts Department.
In evaluating the different locations of the temples, I found a site not mentioned on any of the 19th, 20th or 21st-century maps.
This monastery is found on the sketch and the draft map from Kaempfer and indicated with two stupas. It stood on the west bank of Khlong Makham Riang (1) opposite Wat Tha Pho and north of Pom Phet and the Nai Kai Bridge. There was a bridge in the immediate vicinity linking this temple with Wat Tha Pho.
A 2007 Fine Arts Department map shows the remnants of Wat Tha Pho in geographical coordinates: 14° 20' 53.46" N, 100° 34' 33.10" E, but I believe these are likely the remnants of the opposite temple I call Defunct Temple (4).
The defunct monastery does not feature on any other maps.
The site must have been approximately in geographical coordinates: 14° 20' 52.96" N, 100° 34' 32.59" E.
Footnotes:
(1) Khlong Makham Riang, or the Canal of the aligned Tamarind Trees, was before called Khlong Nai Kai. It is a still existent canal situated east on Ayutthaya's city island. The canal was a shortcut in the oxbow of the old Lopburi River. It has today its origin at Khlong Ho Ratana Chai below Wat Senasanaram and the Front Palace, and its mouth at the present Chao Phraya River, west of Phet Fortress. At the mouth was one of the eleven water gates of Ayutthaya called Pratu Nai Kai. The southern exit, which has today a water regulator, has been altered. The original mouth of the canal was about 170 metres more south, close to Pom Phet. Khlong Makham Riang is one of the three large canals running north to south, of which two still are in existence.