Ban Chai Nat was a strategic outpost of the San Buri (present Sankha Buri) area. It was situated at a bifurcation of the Chao Phraya River, 50 Km
south of Nakhon Sawan. At Ban Chai Nat, the main river split up in two distributaries; the western distributary called today the
Noi River and the
eastern distributary called the Chao Phraya River, on which the Chao Phraya Dam is situated. The whole area of Chai Nat was of military
importance as a couple of kilometers north of Ban Chai Nat, the Tha Jin River split off from the Chao Phraya River in today's Hat Tha Sao
Noting the number of important ancient locations - Chai Nat, San Buri, Choeng Klat, Pho Sangkho (old Sing Buri), Wiset Chai Chan (old Ang
Thong) etc - along the Noi River, I believe that the western arm was considered the main river during the Ayutthaya era. The denomination of the Noi
River, likely came after the western arm silted up, becoming shallow for water transport, while the eastern arm gained prevalence. In the Ayutthaya
era, the western arm was called after the main area where it flows through, being Mueang Phraek Sri Racha.

Prehistoric artifacts such as stone tools, fragments of iron tools, bronze bangles, beads and objects related to ancient rituals and beliefs were found
here. Chai Nat is situated between the Dvaravati sites of U-Taphao (Manorom District, Chai Nat), Dong Khon (Sankha Buri District, Chai Nat) and
Ban Khu Mueang (In Buri District, Sing Buri). Buddha images excavated at Chai Nat and on display at the Chai Nat Muni National Museum are
dating back to the Dvaravati and Khmer period. The area was as thus initially Mon-Khmer. With the rising of the Sukhothai Kingdom ca. 1238, the
area of Chai Nat came under its control. As soon as
King Borommaracha I ascended the throne of Ayutthaya in 1370, he started a campaign against
the Sukhothai Kingdom. Likely around 1371, Ban Chai Nat must have been under Ayutthaya's control as the Royal Chronicles of Ayutthaya mention
that King Borommaracha I invaded Sukhothai and captured several northern towns.

Chai Nat on Valentyn’s map (1726)

Ban Chai Nat is shown on Valentyn’s map "Groote Siamse Rievier Me-Nam Of Te Moeder Der Wateren In haren loop met de vallende
Spruyten Verbeeld
" published in his work "Oud en Nieuw Oost-Indiën" Volume 3, Part 2, Book 6, Chapter 1. A pen drawing of the area shows
some temples and houses on the east and west bank of the eastern arm (present Noi River) as on the east bank of the western arm, which indicates
the area already well populated at the time of making the drawing. The temple on the east bank of the western arm can possibly be Wat Phra
Wat Phra Borommathat Worawihan

Ban Chai Nat was situated where today stands Wat Phra Borommathat Worawihan. Originally the Chao Phraya River split west of Wat Phra
Borommathat, and the present origin of the Noi River, situated east of the temple, is a man-dug canal.
On the premises stood initially a laterite prang dating back to the Mon-Khmer period and housing relics of the Buddha. The stupa was renovated in
the Ayutthaya and Rattanakosin periods and features the characteristics of the U Thong architectural style (a small stupa - Early Ayutthaya period).
The U Thong art flourished in Central Thailand in the 12th - 15th centuries. The architectural style of the U Thong Period is rather obscure, but the
Borommathat Chedi is one of the remaining examples. The monument displays a mingling of Sukhothai and Srivijayan styles. The Sukhothai style is
represented by the bell-shaped stupa, while the Srivijayan style is found in the superimposed redented square base with four porches and particularly
a series of stupika, small chedis used as decorative elements of the stupa. A seated Buddha statue in cross-legged posture and protected by a
seven-headed naga in the Lopburi art style (12th - 13th C AD), found in the porch of the Borommathat Chedi, can be seen at the Chai Nat Muni
National Museum in its immediate vicinity. A stone inscription dating back to the reign of King Phumintharacha (reign 1709-1733) and containing
information about the renovation of the chedi can be found in situ. [1]
The vihara was constructed in the eastern direction behind the main stupa as usual. The monastic structure with a three-tiered roof has undergone
different renovations over time and measures now about 24 by 13 meters. The vihara contains a well, at present covered with glass. The ordination
hall stands south of the vihara on a parallel line. The ubosot measures 24 by 9 meters and has been renovated several times. The main Buddha image
is in the Sankha Buri style (U Thong A / 1250- 1300 AD). The boundary stones of the hall are in the Ayutthaya style. Following the ranking system
for royal temples initiated in 1913, Wat Phra Borommathat bears the suffix 'worawihan' and is as thus a second-class royal temple of the fourth grade.
Chai Nat in the Royal Chronicles of Ayutthaya

History relates that King Intharacha I (reign 1409-1424) had three sons, named according to the old numerical system (Ai = first, Yi = second and
Sam = third). On the death of their father, in 1424, the two elder sons, Ai Phraya living in Suphan Buri, and Yi Phraya living in San Buri, fought for
the throne of Ayutthaya. Both princes engaged each other in personal combat mounted on an elephant on or near the
Charcoal Quarter Bridge
(Saphan Pa Than). Both were severely wounded and died in combat. The youngest brother, Chao Sam Phraya living in Chai Nat, was then
proclaimed King under the title of Borommaracha II. [2]

The King returned to the Capital and then appointed Prince Ai Phraya to live off Suphanburi, Prince Yi Phraya to live off Phræk Siracha,
[F: that is to say, San,] and Prince Sam Phraya to live off
Chainat. (Detail of the Royal Chronicles of Ayutthaya)

Based on the handout of the Chai Nat Muni National Museum and on Chris Baker's "A History of Ayutthaya", the location Chai Nat, where Chao
Sam Phraya ruled, is said to be a settlement on the west bank of the Nan River, opposite Song Khwae (old Phitsanulok), and being the twin city of
the latter. I suppose that this Chai Nat must have likely stood in the area where the foundations of an old palace called "Wang Chan" were
re-discovered in 1995. [3]

I am though not convinced, that Chai Nat was the twin town of Song Khwae. The western part of the Sukhothai dominions (including Chakangrao
and Nakhon Chum) was already annexed by Ayutthaya in 1378. In 1419 King Mahathammaracha III (Sai Luethai) of Sukhothai died. Two brothers
claimed the throne and serious disturbances occurred. King Intharacha I of Ayutthaya advanced to Nakhon Sawan with his army to restore the order
in his vassal state. The show of force was sufficient and the two parties, Phraya Ban Muang and Phraya Ram, arranged their differences. The brother
of King Mahathammaracha III ascended the throne as Mahathammaracha IV of Sukhothai, being a vassal to the kingdom of Ayutthaya. Chao Sam
Phraya was at the same time sent to the said Chai Nat; a strange situation if this location was Phitsanulok as suggested. [4]

If we consider Suphan Buri and San Buri as Mueang Luk (cities of royal children) respectively at a distance of 60 Km and 100 Km from the royal
seat in Ayutthaya, then it looks a bit odd that the third and youngest son - Chao Sam Phraya - would be at a distance of 300 Km from the royal seat
and at 210 Km distance from his elder brother in San Buri. It comes to my mind that the said Chai Nat, could have been the location of the strategic
town of Nakhon Sawan (the location where King Intharacha restored order), situated at the confluence of the Ping and Nan Rivers. The case being,
Chao Sam Phraya would have been located at a distance of 75 Km north of his elder brother in San Buri.

I am thus of the opinion that Chai Nat was wrongly mentioned in this paragraph of the Royal Chronicles; the more that every later mentioning of Chai
Nat in the Royal Chronicles of Ayutthaya, relates to the present area of Chai Nat at the bifurcation of the Chao Phraya River, 50 Km south of
Nakhon Sawan.

Chai Nat Buri is mentioned in the Royal Chronicles of Ayutthaya as the location where King Chakkraphat (reign 1548-1569) in 1552 presided a
Majjhima Kamma", the second step in the inauguration of Brahmans. It indicates the importance of Chai Nat as a Bhramin center, with
Borommathat Chedi and its sacred ablution pond in location. [5]

In 915, a year of the ox] [BCDEF: In 896, a year of the horse, sixth of the decade], in the [A: seventh] [BCDEF: eighth] month, the
Royal Rite of Intermediate [A: Karma] was held for King Cakkraphat in the Municipality of
Chainatburi." (Detail of the Royal Chronicles of

Chai Nat was of strategic importance. In this location, Prince Maha Thammaracha of Sukhothai descended in 1564 with an army of fifty thousand
men from the cities of Phitsanulok, Sukhothai, Sawankhalok, Phichai, and Phichit, in order to prepare for a flanking attack on the Burmese army
besieging the City of Ayutthaya. [6]

In another military event the King of Chiang Mai, executing a decree of the Burmese King, descended south and established an army position at Chai
Nat in 1584 and waited for a congregation with the Phraya of Bassein arriving via Kanchanaburi, in order to attack Ayutthaya. After learning of the
defeat of the Burmese army, and after skirmishes with the Ayutthayan vanguard, the King of Chiang Mai decided to retreat and returned to Chiang
Mai. [7]

Chai Nat was also one of the Ayutthaya strongholds in the Burmese war of 1766-67, kept by Phraya Ammat with 15,000 troops. His position was
overrun by the Burmese. [8]

Simon de La Loubère, a French envoy to the Kingdom in the reign of King Narai, mentioned in his work "
A new Historical Relation of the
Kingdom of Siam
" that there was a custom station at Chai Nat. "On Boats or Balons, the Natives of the Country pay a Tical for every Fathom
in length. Under this Reign they have added that every Balon or Boat above six Cubits broad should pay six Ticals, and that Foreigners
should be obliged to this duty, as well as the Natives of the Country.
" [9]
(Detail of Valentyn's map "Groote Siamse Rievier Me-Nam Of Te Moeder Der Wateren In
haren loop met de vallende Spruyten Verbeeld")
Chai Nat at present

Initially, the strategic outpost of Ban Chai Nat was likely dependent from Mueang Phraek Sri Racha, a city about 15 Km downstream the Phraek Sri
Racha River (today Noi River). Phraek Sri Racha was later called Sankha Buri or shortened San Buri (the sub-district still bears its old name). It
became at the end of the 16th century a proper municipality, as we find for the first time in the Chronicles a "
Phraya of Chai Nat".

During the reign of King Chulalongkorn (1868-1910), the town of Chai Nat was established on the east bank of the Chao Phraya River, opposite
Ban Chai Nat. The importance of San Buri finally declined, as many inhabitants moved to the new town.


[1] Intralib, Sonthiwan - An outline of the History of Religious Architecture in Thailand (Silpakorn University, 1991).
[2] The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) - page 15 / Source: Phan Canthanumat, British Museum, Reverend Phonnarat,
Phra Cakkraphatdiphong & Royal Autograph - King Intharacha, 1409–1424.
[3] Baker, Chris and Phongpaichit, Pasuk - A History of Ayutthaya - Cambridge University Press, 2017 – page 63.
[4] A History of Siam - W.A.R. Wood (1924) - page 79; Wyatt, David K. (2003) - Thailand, A short history (2nd Ed.) - Silkworm Books.
[5] The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) - page 30 / Source: Luang Prasoet, Phan Canthanumat, British Museum,
Reverend Phonnarat, Phra Cakkraphatdiphong & Royal Autograph - Various Events, 1552–1555.
[6] The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) - page 35 / Source: Phan Canthanumat, British Museum, Reverend Phonnarat,
Phra Cakkraphatdiphong & Royal Autograph - War With Hongsawadi, 1563–1564 - Prince Maha Thammaracha of Phitsanulok.
[7] The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) - page 100 / Source: British Museum, Reverend Phonnarat, Phra
Cakkraphatdiphong & Royal Autograph.
Ayutthaya Victory in Chainat.
[8] The Royal Chronicles of Ayutthaya - Richard D. Cushman (2006) - page 495 / Source: British Museum, Reverend & Phonnarat - Ayutthaya
Moves to Counter the Burmese Attack.
[9] de La Loubère (1693) - A new Historical Relation of the Kingdom of Siam (2 Tomes) - London - Edited by John Villiers - White Lotus,
Bangkok, 1986 - page 93 - Of the Barcalon, and of the Revenues.
(Borommathat Chedi)
(Detail of the map "Cours du Fleuve Me-Nam dressé par R.P. Lombard,
missionnaire apostolique de Siam 1878-1879")