Wat Inthawat was a monastery situated off the city island in the eastern area of Ayutthaya, in the Suan Phlu Sub-district. The monastery was named after the Hindu God Indra, King of Devas, God of War and God of Thunder and Storms, called Phra In (พระอินทร์) by the Thai people. [Wat In Dawat]
In situ is a brick mound with - what looks like - some fragmented pieces of sandstone Buddha images. On top of the brick mound is, at present, a vihara with some Buddha statues. The main image is called Luang Pho Thong. The monastery must have been orientated east towards Khlong Thanon Tan.
The site in geographical coordinates 14° 20' 46.72" N, 100° 35' 22.24" E is not mentioned on any Fine Arts Department maps.
I found this site in early February 2012 CE when interviewing a villager near Khlong Thanon Tan regarding Wat Samo. During our chat, the man indicated another old site in the area. He scribbled some directives on a piece of paper, and after our talk, I immediately visited the stated site. I was led by a clever young chap zigzagging between a cluster of houses to a mound on which a vihara stood. The site is locally known as Wat In.
There is a monastery with the same name located on Ko Loi (Floating Island) in the north of Ayutthaya.
Footnotes:
(1) Khlong Thanon Tan or the Canal of the Sugar Road. It flows through the Kramang and Suan Phlu sub-districts. The canal links Khlong Khao San with Khlong Suan Phlu and the Pa Sak River and probably gave access earlier to Wat Yai Chai Mongkhon. No monasteries were situated along its banks. The canal forms an island called "Ko Kaeo" or "Crystal Island", with a stretch of the Pa Sak River and Khlong Khao San. Ko Kaeo was an important battleground during the wars with the Burmese. The canal is filled in and is only used as a water drainage canal (heavily polluted).