Wat Sam Jin on the maps:
Wat Sam Jin could be on Johannes Vingboons drawing "Afbeldinge der stadt Iudiad hooft des choonincrick Siam" dating back to 1665 CE. We can clearly define the area in which Wat Sam Jin is located in the square formed by the connection of four bridges, of which three can be named, the Khun Mueang Jai Bridge, an undefined bridge, the Nai Kai Bridge and the Chinese Market Bridge. In this square, we find five temples, of which the middle one, I presume, is Wat Sam Jin. There is a discrepancy as the canal linking the Chinese Gate Canal, and the Nai Kai Canal is on this drawing north of Wat Sam Jin, while based on the Kaempfer and Phraya Boran Ratcha Thanin maps, it runs south of the monastery. Johannes Vingboons (1616-1670 CE) was a Dutch mapmaker of the 17th century, born in Amsterdam. He was a renowned watercolourist, creating maps with a great deal of accuracy, used for references in libraries and decorating the walls of the houses of the royal families.
Wat Sam Jin shows on Kaempfer’s map. Engelbert Kaempfer (1651-1716 CE) was a medical doctor working for the Dutch VOC (Verenigde Oost-Indische Compagnie) who surveyed the city of Ayutthaya in June 1690 CE. In his sketch, there is an indication of a temple north of the canal linking the Chinese Gate Canal and the Nai Kai Gate Canal (Khlong Makham Riang). However, this canal is not entirely extended to the Nai Kai Gate Canal in the sketch (this canal is even missing from Kaempfer's draft). There is a road leading north from the Ok Kai Fortress towards Pa Thon Road, and we find the temple on the east side of the road. On Bellin’s map, "Plan De La Ville De Siam", we do not find the waterway linking the Chinese Gate Canal with the Nai Kai Canal, but Chinese Street with Phaulcon's lodge is visible as well as the Ok Kai Fortress. From the fortress, we have a road crossing Chinese Street running north to Pa Thon Road. On this road on the east side, we find an indication of a temple, which was likely Wat Sam Jin.
Jacques-Nicolas Bellin (1703-1772 CE) was one of the most important cartographers of the 18th century. He was a hydrographer and 'ingénieur hydrographe' at the French 'Dépôt des cartes et plans de la Marine'. The map "Plan De La Ville De Siam" of the French cartographer Jacques Nicolas Bellin (1703-1772 CE), based on a Jesuit survey in 1687 CE and published as plate No. 4 in volume 9 of the 1752 CE French edition of Abbé Antoine François Prévost's l'Histoire Générale des Voyages.
The 19th-century map by an unknown surveyor shows Wat Sam Jin aligned between the Chinese Gate Canal and the Nai Kai Canal canals. From east to west, we find Wat Tha Ma, Wat Sing Rai, Wat Sam Jin, and Wat Mai. The Chinese Gate Bridge is indicated on this map north of the temple alignment and, in real life, stands south of the alignment, which let me presume that this could be the Wat Khun Muaeng Jai Bridge instead of the Chinese Market Bridge.
Wat Sam Jin appears on Phraya Boran Ratchathanin's map of 1926 CE on the north bank of a waterway linking the Chinese Gate Canal with the Nai Kai Canal and giving access to a swamp adjacent to Wat Khun Mueang Jai. This swampland is still visible behind Wat Sam Jin. Further east stands Wat Sing Rai. Phraya Boran (1871-1936 CE) was the Superintendent Commissioner of Monthon Ayutthaya from 1925 till 1929 CE.
A 2007 digital Fine Arts Department map indicates Wat Sam Jin, also as Wat Thanon Jin.
The ruin of Wat Sam Jin is in geographical coordinates: 14° 20' 59.16" N, 100° 34' 21.84" E.
Footnotes:
(1) The temple refers likely to the three gods found in nearly every Chinese home and many Chinese-owned shops. The gods are Good Fortune (Fu), Prosperity (Lu), and Longevity (Shou).
(2) Most southern point of the city island including the harbour and opposite Wat Phanan Choeng. Hua Ro was the most northern point, and Hua Laem was the island's most western point.