Ajahn Mun dark Did Ajahn Mun say the Buddha congratulated him on the night he attained arahant? His biography books says it for sure. Venerable Ācariya Mun Būridatta Thera is one of the most revered forest masters of the 20th century. He is the root guru of both the Dhammayut and Ajahn Chah monasteries. He popularized the monastic practice of living under an umbrella in the forest and his relentless energy is fascinating and inspiring.