Richard Paine qualified (MRCVS) in 1901 and joined the Veterinary Service of the Cape Colony in 1902. He was stationed consecutively at East London, Beaufort West, and the Agricultural School at Elsenburg, Stellenbosch, where he was appointed resident lecturer in animal hygiene in 1908. At the same time he held an appointment as veterinary officer, with the honorary rank of lieutenant, in the Western Lieutenant Horse regiment. In 1904 he performed inocculation experiments to test his hypothesis that "Geeldikkop" is an insect-borne disease of a malarial nature, but the results were negative. The work was published in the Reports of the Chief Veterinary Surgeon... for 1904, and two years later in the Journal of Comparative Pathology and Therapy. He obtained his FRCVS in 1907 with a thesis entitled Clinical notes upon some poisonous plants in the Cape Colony. For his services he received two letters of appreciation from John X. Merriman, prime Minister of the Cape Colony. Also in 1907 he published an article on "Johne's disease" (chronic bacterial enteritis of cattle) in the Agricultural Journal of the Cape Colony (Vol. 31, pp. 160-162). A paper which he read before the Paarl Farmers' Association, on "Tuberculosis in cattle", was published in the Natal Agricultural Journal (Vol. 11, pp. 1401-1410) in 1909.
Paine was a member of the Royal Sanitary Institute. In November 1905 he was one of the founding members of the Cape of Good Hope Veterinary Medical Society, served on its council from the society's formation to at least 1913, and as honorary secretary and treasurer in 1910-1911. He later joined the Transvaal Veterinary Medical Association and in 1920 transferred his membership to the newly formed South African Veterinary Medical Association.
In 1922 he was transferred to the Grahamstown Veterinary Laboratory where he did pioneering work on tuberculosis in wild animals. In 1934 he took charge of the Allerton Laboratory in Natal until his retirement in 1939. He then started a practice in Pietermaritzburg which he maintained until 1947. After the death of his first wife, Florence, in 1917, he married Elsie E. Root. His son, B.T. Paine, also became a veterinarian.