Wat Rak or the "Monastery of the Crown Flower" was situated on Ayutthaya's city island in the Historical Park in Pratu Chai sub-district. The temple was located on the east bank of Khlong Chakrai Yai, called Khlong Tho in its northern stretch.
On its south stood Wat Chana Man (no traces anymore); opposite Khlong Chakrai were Wat Kao (no traces anymore) and Wat Khun Phrom. In the east stood Wat Pa Mo (no traces anymore), the name at par with Khlong Pa Mo, a canal running just south of the temple, being an extension of Khlong Klaep/Khlong Tha Phra.
There are no traces of foundations or brick work at ground level and the temple is classified as disappeared.
Historical data about the monastery and its construction is unknown.
The monastery was likely named after the Calotropis Gigantea or Crown flower, a species of Calotropis native to Cambodia, Indonesia, Malaysia, Philippines, Thailand, Sri Lanka, India and China. It is a large shrub growing to 4 m tall. Its flowers are strung into garlands to be worn around the necks of criminals on their way to the place of execution. In Thailand the Rak tree grows wild in deserted dry places. Its trunk and branches have a milky sap and its flowers are used for floral pieces which are to be seen usually at cremations. Today it is the fashion for a bride and groom to wear a garland of these flowers, for the name "rak" means "love" in Thai. 
 Some Siamese Superstitions about Trees and Plants - Phya Anuman Rajadhon - JSS Vol 49.1 - 1961 - page 58.
Text & maps by Tricky Vandenberg - October 2009 Reviewed February 2011, January 2013