Ralph S.G. Stokes interrupted his private education to come to South Africa to take part in the Anglo-Boer War (1899-1902) as a trooper in Paget's Horse. After the war he was employed by H. Eckstein and Company as a sampler and assistant surveyor on the Crown Reef Mine. A part-time position as mining editor of the Rand Daily Mail enabled him to continue his studies and to tour the mines of the British Empire, leading to a series of articles in the newspaper during June 1906 to September 1907. He also wrote a report entitled Malay tin-fields; mining position broadly reviewed (Singapore, 1906, 40 pp.) and a substantial book, Mines and minerals of the British Empire (1908, 403 pp). In 1907 he again joined H. Eckstein, assisted with the valuation of the New Modderfontein Gold Mining Company, and worked on the Robinson Mine, Crown Mines, and in Eckstein's administration. He presented specimens to the museum of the Geological Society of South Africa in 1907. A few years later, in collaboration with J.E. Thomas*, G.O. Smart*, W.R. Dowling*, H.A. White*, E.H. Johnson*, W.A. Caldecott*, A. McA. Johnston*, and C.O. Schmitt*, he wrote A textbook of Rand metallurgical practice (London, 1912, 2 vols).
From 1912 to 1914 Stokes worked as a field engineer for the International Nickel Company of New York. During World War I (1914-1918) he was on active service in France as Controller of Mines, with the rank of Colonel. Thereafter he was chief engineer of the Expeditionary Forces in north Russia during 1918-1919. In recognition of his work during the war he was awarded the Military Cross (MC, 1916), the Distinguished Service Order (DSO, 1917) and the Order of the British Empire (OBE, 1919). In 1920 he returned to South Africa and became superintendent of mines and assistant general manager of De Beers Consolidated Mines at Kimberley. In 1928 he returned to Johannesburg to join his old firm, which had meanwhile become The Central Mining and Investment Corporation, as consulting engineer and technical director. He became a director in 1944 and served on the board until 1959. During World War II (1939-1945) he served in the Western Desert as chief engineer in charge of the construction of airfields with Montgomery's Eighth Army, attained the rank of Brigadier, and was honoured as Commander of the Order of the British Empire (CBE, 1942).
Stokes served on the council of the Geological Society of South Africa from 1929 to 1939 and as its president in 1934. His presidential address, 'The geological surveys and societies of the world', was published in the Proceedings of the Geological Society of South Africa (1935, pp. xxiii-xlii). He was a corresponding member of council of the Chemical, Metallurgical and Mining Society of South Africa as early as 1913, served as joint vice-president from 1934, was elected president for 1937/8 and was elected an honorary life member in 1946. His presidential address dealt with the financial aspects of mining on the Witwatersrand. In 1954 he was president of the (British) Institution of Mining and Metallurgy and in his presidential address discussed 'Future resources and problems of the Witwatersrand Gold Field'. After his death the South African Institute of Mining and Metallurgy (successor to the Chemical, Metallurgical and Mining Society of SA) established the Brigadier Stokes Memorial Award to recognise outstanding contributions to the mining industry.
Stokes was a man with a superior intellect and inexhaustible energy who travelled widely, had many friends, and was informally known in his later years as 'The Brig'. In 1921 he married Lora Mary (Molly) Bradford, with whom he had four daughters.