The distinctive feature of the Phra Khun Phaen coating at Wat Yai Chai Mongkhon is the lacquer coating, which is applied only to the front side. The color tends to be in shades of brown because it is only applied to the front. The coating is created from a mixture of white clay and lime..
There are two main pims: Pim Ok Yai and Pim Kaen both inside a glass enclosure, the buddha image sitting in the Maravichi posture exhibiting qualities of compassion, mercy, and greatness, known as “Krop Jakrawan”. Additionally, other sacred images, such as the red-copper Phra Khun Phaen Shin Thakrawan and Khun Paen Bai Phutsa in both clay and metal.
This amulet is often classified as the prototype to todays modern Khun Paen pims, this amulet is over 300 years old and was consecrated during the reign of King Narusuan the Great
It is believed that the Phra Khun Phaen coating was created by Phra Phanarat, a teacher of King Naresuan the Great, and was enshrined in the main stupa during the occasion when King Naresuan the Great challenged and defeated the Burmese forces. He then built the Great Pagoda as a memorial at Wat Pa Kaeo, which is now Wat Yai Chai Mongkhon.
The Phra Khun Phaen coating is not only found at Wat Yai Chai Mongkhon but also in various other temples. However, they do not have the same lacquer coating but share the same mold as Wat Yai Chai Mongkhon. In 2506, at Wat Chong Tha in Nonthaburi province, similar molds were found, but the lacquer was clearer and less intense compared to those at Wat Yai Chai Mongkhon.
Clandestine excavation of the temple for artifacts in the year BE 2478 resulted in The Fine Arts Department declaring Wat Yai Chai Mongkhon as a national historical site, and in 2499, Phra Khru Phawanarangsi (Phra Rong Chaiyan) took charge of the restoration of the pagoda. Monks also began to reside and observe the rains retreat (Phansa).
In 2500, Phra Khru Phawan requested cooperation from the Fine Arts Department to conduct further excavation. Golden Buddha images were found beneath the central base of the pagoda along with evidence that treasure hunters were still actively pilfering sacred artifacts. Eventually, a joint resolution with the Fine Arts Department was made to cease all excavations and fill the holes with concrete reinforced with steel to prevent further clandestine excavations.
During the Ayutthaya period, this temple was built during the early reign of King Ramathibodi I, also known as King U-Thong, the founder of Ayutthaya. Legend has it that in the year 1900 of the Buddhist calendar, King U-Thong graciously ordered the excavation and cremation of the bodies of Lord Kaew and Lord Thai, who died of an incurable disease. He then ordered the establishment of a monastery named Wat Pa Kaew (Pa Kaew Forest Monastery). Subsequently, a group of monks from Sri Lanka, who had completed their studies at Ratanamahathat Monastery in Sri Lanka, came to be greatly revered by the people of Ayutthaya.
This led to an influx of people coming to ordain and study at the monastery, leading King U-Thong to establish a new sect called the Nikaya Sangha and appoint a Sangharaja (ecclesiastical head) for this sect, named Sangharaja Phra Wannarat. He held the position of the Sangha’s right-hand preceptor alongside the Sangharaja Phra Phutthakosajarn, who held the position of the Sangha’s left-hand preceptor. Later, he became the teacher of the monks of Wat Pa Kaew Monastery, and because of this, the monastery came to be known as Wat Chao Phraya Thai Nikaya Pa Kaew.
The Victory Pagoda, a monument of glorious triumph, was erected to commemorate the victory of His Majesty King Ramathibodi over the Mon Kingdom of Myanmar. It is believed that the construction of the Chai Mongkol Pagoda was inspired by this historic event.
During that time, the Mon forces invaded the borders of Thong Seema, Nong Sarai Subdistrict, Suphanburi Province. His Majesty King Ramathibodi and His Majesty the Crown Prince, who was a sage prince, led the army to confront the enemy. They fought valiantly, with His Majesty even mounting an elephant and entering the fray surrounded by a group of soldiers, shooting guns and arrows at the enemy. The enemy soldiers, who were unable to keep up with His Majesty’s pace, were defeated. His Majesty then declared loudly that he would stand under the shade of a tree to await the enemy’s challenge to battle. He declared that henceforth, no king would have the right to challenge him to battle. Subsequently, the Mon King emerged on an elephant to challenge His Majesty to battle. In the ensuing battle, His Majesty King Ramathibodi used his divine light to defeat and drive off the Mon King.
Wat Yai Chai Mongkhon is located in Tambon Khlong Suan Phlu, Amphoe Phra Nakhon Si Ayutthaya, Phra Nakhon Si Ayutthaya Province. The highlights of the temple include the newly renovated grand pagoda and the interior containing the sacred image of Phra Phuttachai Mongkhon. The principal image is a sacred symbol of the temple and is a significant tourist attraction in Phra Nakhon Si Ayutthaya Province.