Anuradhapura, the ancient capital of northern Sri Lanka. Here, the true history of Buddhism in Sri Lanka began during the reign of King Devanampiyatissa, who ruled from 236-276 CE. Mahintale or Missaka Mountain is the place where the Pali scriptures state that a group of monks led by Mahinda Thera, the son of King Ashoka, along with four other monks, traveled from India to spread Buddhism in Sri Lanka for the first time. When Buddhism was established in Sri Lanka, King Devanampiyatissa built a “monastery of the great temple” in the middle of Anuradhapura, which became the name of the group of monks called the “great temple group”, with Thuparam Stupa as the first stupa built in Sri Lanka. Sri Lanka entered another important era in the history of Buddhism after King Vattakamani Aphaya ascended to the throne in 439 CE. Soon after, the Tamils ​​seized power. And occupied Anuradhapura for 14 years. During this time, the country was in a difficult period to the point of having to eat human flesh. The great monks were afraid that the religion would disappear, so they agreed to hold a meeting to recite the Dharma and Vinaya at the Alokalena cave in the Malaya countryside, with King Vattakamani Abhaya as the patron. The Buddha's words were recorded in writing on palm leaves for the first time after the previous method of memorization for more than 400 years after the Buddha passed away. During the reign of King Vattakamani Abhaya, he built a temple to dedicate to the great monk Mahatissa, who helped him during the war with the Tamils. This became the beginning of a new sangha called "Abhayagiri Vihara", apart from the original Mahavihara sect. It was also the beginning of the rift with the Mahavihara sect because the Mahavihara sect was a group that adhered to the teachings and traditions, and despised monks from other sects as immoral. While the Abhayagiri Vihara sect was known as a group with independent opinions, welcoming new perspectives, studying both Theravada and Mahayana sects. The Abhayagiri Vihara Sect thus became an important center of Mahayana in Sri Lanka. During the 12th to 17th Buddhist centuries, Sri Lanka was in turmoil due to the invasions of Timla in India and internal unrest. During this period, the nuns’ sect disappeared, and the monks’ sect itself began to decline. However, Buddhism in Sri Lanka continued to move forward. The great decline of Buddhism occurred when the Portuguese settled in Sri Lanka in 2048, and eventually conquered Sri Lanka, which severely affected Buddhism. During the reign of King Vimol Thammasuriya I, who ruled from 2137 to 2147, the center of power in Sri Lanka was “Krung Sirivattanaburi” or the present-day city of Kandy. He had the idea to revive Buddhism because at that time there were no monks left in the entire island of Sri Lanka. He sent an ambassador to Burma to request a group of 10 monks to perform the ordination ceremony in Sri Lanka in 2140. But when the Portuguese invaded Kandy, he had to flee into the forest, causing Kandy to fall to the Portuguese in 1611, which caused Buddhism to decline again. It was not until the reign of King Singh II, who ruled from 1635 to 1687, that he asked for help from the Dutch to drive the Portuguese out of Sri Lanka. Finally, the Portuguese base at Colombo was defeated in 1656. During the reign of King Vimol Thammasuriya II (1687–1707), he intended to revive Buddhism again. However, at that time, there were fewer than 5 monks in Sri Lanka who could perform the ordination ceremony. Therefore, he sent a second envoy to invite the Burmese monks to help in the ordination ceremony again in 1697. However, after the Burmese monks established the religious dynasty for a short time, Buddhism in Sri Lanka began to decline again until the monks almost lost their monastic lineage. There was only one novice left named “Saranangkorn”. King Kirati Srirajasingha reigned from 2290 to 2325. He realized the decline of Buddhism, so he sent an ambassador to Ayutthaya to request a monk to help ordain and revive the religion for the Sinhalese children. In 2293, King Borommakot chose Phra Ubali Mahathera and 24 monks to travel by ship from Ayutthaya to Sri Lanka. The ambassadors from Ayutthaya stayed at Wat Buppharam or Wat Malwatta. The ordination ceremony at that time was presided over by Phra Ubali Mahathera. Six novices, including Samanera Saranangkorn, who was about 40 years old, asked to be ordained as a monk. Later, Phraksu Saranangkarnang was also the first Sangharaja of the Siamwong sect in Sri Lanka. During about 3 years in Sri Lanka, Phra Ubali Thera and his group ordained more than 700 Sri Lankan monks and 3,000 novices. Later in 2298, King Borommakot also graciously sent the second group of 60 Sangha missionaries to Sri Lanka to further strengthen the Siamwong Buddhism. Phra Ubali Maha Thera fell ill and passed away in 2299, only 4 years after his arrival in Sri Lanka, completing his mission of helping to spread Buddhism between the two lands. Even though in the past, Siam accepted Buddhism from Sri Lanka as a part of its society until it became the “Lankawong,” in the end, The seeds of Dharma from Siam were brought back to be planted as new seedlings that flourished in Sri Lanka called “Siam Wong”. It is gratifying that Sri Lankans today continue to help water, till the soil, and support the seedlings of Buddhism to grow and take root firmly and strongly until today.