Wat Khok Yai Ma was located on the city island in the southern part of Ayutthaya in the Pratu Chai Sub-district, east of Somdet Phra Sri Nakharin Park, and the location is still part of the Ayutthaya Historical Park.
The monastery was situated between Khlong Chakrai Yai (1) and Khlong Pratu Chai (2).
Wat Khok Yai Ma stood east of Wat Hip and west of Wat Khok Khemi and Wat Khok Yai Mi, which stood opposite Khlong Pratu Chai. The temple stood west of the present Ayutthaya Hospital.
There are no traces of the monastery above ground level, though there could be a possibility that the ancient well was once part of the monastery.
Historical data about the monastery and its construction are unknown.
The mapping carousel
Wat Khok Yai Ma does not show on the 19th-century map. Wat Prasat and Wat Khok Yai Mi do.
Wat Khok Yai Ma is also not indicated on Phraya Boran Ratchathanin's (PBR) map drafted in 1926 CE. We find the above Wat Khok Yai Mi close to the present Chao Phraya River and Wat Khok Khema east of Wat Khok Khemi, both north of Wat Khok Yai Mi. PBR adds as thus two more temple locations.
A 1993 CE FAD map starts the confusion. The map shows Wat Khok Khemi, Wat Khok Yai Mi and adds Wat Khok Yai Ma, not mentioning Wat Khok Khema anymore. There seems to happen a carousel of the temple names. The location of Wat Khok Khema is renamed Wat Khok Yai Mi, while the site of Wat Khok Yai Mi is renamed Wat Khok Yai Ma. Wat Khok Khemi and Wat Khok Yai Ma are aligned north-south, and wat Khok Yai Mi stands east of them.
On the 2007 CE FAD map, we find the three temples, Wat Khok Khemi, Wat Khok Yai Mi and Wat Khok Yai Ma, confirmed as on the 1993 FAD map. Be aware that Wat Khok Khemi and Wat Khok Yai Mi do not belong to the Ayutthaya Historical Park.
I have no idea why PBR’s Wat Khema was changed into Wat Khok Yai Ma and why there was a turnabout of the temple locations. Following PBR, the temple's location here discussed should be Wat Khok Yai Mi, as it is the closest to the main river and west of the defunct Victory gate Canal (Khlong Pratu Chai).
Some remains of the temple were excavated by the Fine Arts Department (FAD) in geographical coordinates: 14° 20' 33.30" N, 100° 33' 30.38" E (based on the 2007 CE map).
Wat Khok Khema
The temple was situated north of what PBR mentions as Thanon Rong Krai (street). On his map, Wat Khok Khemi and Wat Khok Khema are situated in a cluster on a mound, as part of their names indicate (Th: Khok = mound).
The monastery has been named after Khema, one of the two chief female disciples of the Buddha (the other being Uppalavanna). Khema was the daughter of the chief of the Madra group living in Punjab. Madra princesses were favoured for their beauty, and Khema was no exception. The colour of her complexion was that of gold, and she was gorgeous. She married King Bimbisara from the Haryanka dynasty (reign 543-491 BCE), one of the early kings of the ancient Indian kingdom of Magadha, strategically located on the Ganges River (now west-central Bihar state, in northeastern India). The king was a supporter of the Buddha, and she became one of his three chief queens. Encouraged by her husband to meet the Buddha and listen to his sermons, she attained full enlightenment and became an arahant. With the king's permission, she joined the order of nuns.
Footnotes:
(1) Khlong Chakrai Yai is part of a waterway running through the west of Ayutthaya from north to south. The canal was the extension of Khlong Pak Tho and ran from the Lam Hoei Bridge to the Chakrai Yai Gate opposite Wat Phutthaisawan. The canal was a shortcut through the oxbow of the Lopburi River and connected the old Lopburi River, present Khlong Mueang in the north with - what is today - the Chao Phraya River in the south. Ban Chakrai was a village located on the city island but outside the city walls.
(2) Khlong Pratu Chai, or the Victory Gate Canal, is a defunct canal situated on Ayutthaya's city island in the Pratu Chai Sub-district. The north-south running short canal had its mouth at the old Lopburi River (in 1857 CE deviated Chao Phraya River today) in front of Wat Tha Rap and linked up with a canal connecting Khlong Chakrai Yai and Khlong Chakrai Noi. The canal pierced the fortified city wall at the Victory Gate, a large water gate between Wat Khok Khemi / Wat Khok Yai Mi and Wat Prasat. The canal was filled up somewhere after the fall of Ayutthaya (1767 CE), and no traces of the waterway are left today. Khlong Pratu Chai must have run on today's premises of Ayutthaya Hospital.