Venerable Phra Ajahn Tong Sirimangalo was born in 1923 and has dedicated his life to the practice and transmission of Vipassana meditation. In 1934 he ordained as a novice and in 1944 he received full monastic ordination. In the 1950s, he was the only representative of the Northern Thai Sangha sent to Wat Mahathat in Bangkok for one year to learn Vipassana meditation based on the four basics of mindfulness for one year. This was followed by two years of teaching and practice in Burma, including with Venerable Mahasi Sayadaw Bhaddantasobhana Mahathera. Venerable Phra Ajarn Tong Sirimangalo is a highly respected meditation teacher in Thailand. Since the early 1980s, he has also led Vipassana courses in Europe and America. Mostly he lived and taught at Wat Phradhatu Sri Chom Tong Voravihara near Chiang Mai in Thailand. This is a large and well-known meditation monastery, which he headed as abbot and which also has an international center for foreign practitioners. The latter is headed by Khun Thanat and Khun Kathryn Chindaporn. On December 13, 2019, at the age of 96, our highly esteemed teacher left this world. We are grateful for the years of teaching and tireless support that the Most Venerable Phra Prom Mongkol Vi has given so generously to so many.