During excavations in situ, a kiln was discovered, which led to the assumption that the bricks for the monastery's construction were made on location. Kilns in situ were also found, for example, at Wat Phutthaisawan. (4)
Wat Jong Krom is only found on recent Fine Arts Department maps and bears here either the name Wat Jong Krom (วัดจงกรม - 1993 map) or Wat Jong Klom (วัดจงกลม - 1974, 2007 maps). The ruins are in geographical coordinates: 14° 22' 28.63" N, 100° 33' 19.04" E.
Footnotes:
(1) Thung Khwan, or "Field of Fumes", is an area north of the city of Ayutthaya bordered on the north by Thung Lum Phli, on the east by Khlong Sra Bua and Thung Kaeo, in the south by the old Lopburi River and in the west by Thung Phukhao Thong.
(2) Khlong Sra Bua, or the Lilly Pond Canal, is situated in the northern area, off the city island, in the Khlong Sra Bua District. The waterway splits from Khlong Hua Ro between Wat Ngiu (defunct) and Wat Si Liam. The canal has its mouth at the City Canal (Khlong Mueang) between Wat Na Phra Men and Wat Mai in front of the northeastern corner of the Grand Palace. The canal was a shortcut in the old Lopburi River.
(3) จงกรม = to walk back and forth. The Fine Arts Department mentions ‘Wat Jong Klom’ in situ, but I presume it is ‘Wat Jong Krom’ as indicated on the 1993 FAD map.
(4) Issue explained by Prof. Bidya Sriwattanasarn in location on 26 June 2010.
References:
[1] Döhring, Karl (1920). Buddhist temples of Thailand (Buddhistische Tempelanlagen in Siam).