Professor E.H.S. Simmonds was born in 1919 at Littlehampton, Sussex. He was educated at Lord Weymouth's school, Warminster. He was enrolled into a course that sponsored by the Institute of Bankers in 1937 because his father want him to be a distributor of agricultural machinery and farming supplies. But Simmonds enlisted in the ranks of the Royal House Artillery and was commissioned in 1940. He was involved in the Malayan Campaign and the surrender of Singapore. He spend four years as a prisoner of war in Singapore and Thai camps. After returning to England, he went to Keble College Oxford in 1946 to study English Language and Literature. However Simmonds continued to be interested in the Thai people and their culture, thus, leading to him teaching linguistics at the School of Oriental and African Studies, London, from 1948. He remained at SOAS until his retirement in 1982 from the position of Professor of the Languages and Literatures of South East Asia.
Simmonds played also a major role in the Royal Asiatic Society. He became a Fellow in 1954 and served as Director (1965-68), Vice-President (1968-72 & 1976-80) and President (1973-76). He was married to Patricia Simmonds, actress and artist. He died in 1994.