Wat Ko Kaeo, or the Monastery of the Crystal Island, is an active temple located off the city island in the eastern area of Ayutthaya in the Kramang Sub-district. The monastery is situated on the east bank of the Pa Sak River on an island formed by Khlong Khao San (1) in the north and Khlong Khanom Tan (2) in the south, and confluence at the mouth of Khlong Dusit (3).

The temple can be reached by taking Road No 3477, south of the Pridi-Thamrong Bridge and parallel with the railway. North of the temple is Wat Kluai, and further south lies Wat Phanan Choeng. Opposite the monastery on the west bank of the river lies Wat Rattanachai (Wat Jin).

In situ is a large and prosperous monastic complex. The ordination hall stands in the classic east-west alignment facing the Pa Sak River. The ubosot, built in the late Ayutthaya style (1629-1767 CE), has two elevated porches, each with four columns supporting the two-tiered roof. Each porch has two entries. The southern and northern walls have five rectangular windows. An inner wall surrounds the structure, called Kamphaeng kaeo (crystal wall), separating the monastic and secular worlds. The site has numerous chedis and open-sided pavilions (sala).

A shrine is dedicated to King Taksin, commemorating his escape from the area here through the Burmese encirclement in December 1766 CE and his come back to the former warzone after the fall of Ayutthaya in 1767 CE to oust a Burmese proxy at Pho Sam Ton and to restore the internal order in Siam. He established the capital in Thonburi and reigned for 15 years. The monastery was re-established in the early Rattanakosin period, during the reign of Rama I.

Ko Kaeo, or Crystal Island, is mentioned a few times in the Royal Chronicles of Ayutthaya. Ayutthaya was on three sides surrounded by the Lopburi River, but the eastern city border was its weakest point in 1568 CE, as at that time there was only a moat between the Rattanachai Gate in the north and Kaeo Island in the south. (4)

We read in the chronicles: "The officials and men of all the cities of Chainat, Suphanburi, Lopburi, Inburi, Phetburi, Ratburi, Nakhon Nayok, Saraburi, Phromburi, Sanburi, Singburi, Nakhon Chaisi, Thonburi, and Marit occupied the positions from the Ratanachai corner down to Kaeo Island the side so constituted, not being separated by the river from the land, had only a moat." [1]

The Burmese, preparing for the attack on Ayutthaya, made earthen causeways towards the Siamese front ramparts at three points. One of these points was the corner of Ko Kaeo, where the King of Ava was positioned.

"When the inventory of all the troop supplies ordered by the King was completed, the King of Hongsawadi had preparations made for attacking the Capital and ordered causeways laid extending in towards the front ramparts of the city from three points from the positions of the Uparat the first was to be laid extending in to Fang Monastery and a second to Ian Village, and from the positions of the King of Ava a third was to be laid extending in to the corner of Kæo Island. In laying the earth in towards the city the men of Hongsawadi constructed shields and set them up running in towards the city to protect themselves from firearms, and they heaved the earth on ahead over the shields." [2]

The Siamese on Crystal Island could not withstand the Burmese land attack, additionally supported on the flanks by a naval force (likely on both canals surrounding Ko Kaeo). The Siamese fled into their enclosure, and the wall on the corner of the island was penetrated and destroyed. The loss of Crystal Island would finally lead to the first fall of the City of Ayutthaya in 1569 CE.

“Meanwhile, Phraya Ram, Phra Kalahom and Phra Maha Thep seeing the army being protruding towards them, ordered the erection of one-storied, semicircular stockades on the ramparts of the Capital and brought up cannon and monthok guns to be set up in abundance in the face of the stockades. The troops at their posts on the walls and earthworks still fought on to defend the city. The King of Hongsawadi had his troops brought in along the causeway at the corner of Kæo Island, had the naval forces brought in on the flanks, and had carong, monthok, and trigger guns fired in salvos like a rainstorm at the officials in order to seize the Kæo Island corner. The picked troops stationed at the Kæo Island corner, unable to fight and defend themselves, fled down into the stockade which they had established, and the men of Hongsawadi managed to penetrate to, and destroy, the wall at the Kæo Island corner.” [3]

Phraya Boran Rachathanin wrote in the late twenties of the last century that the ordination hall of the monastery at that time had collapsed nearly entirely in the water.

There was a boat ferry between Wat Ko Kaeo and the landing at Wat Suwan across the river. [4]

Wat Ko Kaeo is indicated on Valentyn's map "Groote Siamse Rievier Me-Nam Of Te Moeder Der Wateren In haren loop met de vallende Spruyten Verbeeld" as Wat Kokeuw. [5]

We find the monastery on a 19th-century CE map and Phraya Boran Rachathanin's map drafted in 1926 CE.

The monastery is in geographical coordinates: 14° 20' 49.92" N, 100° 34' 60.00" E.


(1) Khlong Khao San, or the Canal of the Milled Rice, flows on the border between Phai Ling and Suan Phlu sub-districts. It links Khlong Dusit with the Pa Sak River. At par with Khlong Hantra, Khlong Kramang and Khlong Dusit, this canal was probably once a stretch of the Pa Sak River. This canal is also referred to as Khlong Ko Kaeo. (2) Khlong Khanom Tan or the Canal of the Sugar Candy (a). It flows through 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). (a) A dessert made from rice flour mixed with yeast, coconut milk, ripe palm fruit, and sugar, put in a krathong or wrapped in banana leaves, sprinkled with shredded coconut, and steamed.

(3) Khlong Dusit flows through the Phai Ling Sub-district. Like Khlong Hantra, Khlong Kramang and Khlong Khao San, this canal was likely once a stretch of the Pa Sak River.

(4) After the first fall of Ayutthaya in 1569 CE, King Maha Thammaracha consulted his "lessons learned" and widened the moat for military purposes. This moat was called "Khu Khue Na" or "Khu Na Muang" (Front City Moat). The former moat is said to have been dug during the reign of King Ramathibodhi I (1351-1369 CE). It was initially a defensive moat or could have been a separation ditch (borderline) between the ancient city of Ayothya, situated in the oxbow of the Pa Sak River, and the newly established city of Ayutthaya in the oxbow of the Lopburi River.

(5) In Ayutthayan times, there were twenty-two ferry routes. In the eastern area, the four other crossings were: Tha Chang Wang Na to Tha Wilanda, north of Wat Khwang Fortress to Wat Taphan Kluea, south of Wat Khwang to Wat Nang Chi and south of Wat Pa Thon to Wat Phichai. [4]


[1] Cushman, Richard D. & Wyatt, David K. (2006). The Royal Chronicles of Ayutthaya. Bangkok: The Siam Society. p. 60.

[2] Ibid. p. 62.

[3] Ibid. p. 66.

[4] Rachathanin, Phraya Boran. Athibai Phaenthi Phra Nakhon Sri Ayutthaya kap khamwinitjai khong Phraya Boran Racha Thanin. Explanation of the map of the Capital of Ayutthaya with a ruling of Phraya Boran Rachathanin - Revised 2nd edition and Geography of the Ayutthaya Kingdom. Ton Chabab print office. Nonthaburi (2007). p. 91.

[5] Valentyn, François (1626). Oud en Nieuw Oost-Indiën. Deel 3. Boek 6. Beschryvinge van Siam en onsen Handel aldaar.