Thomas graduated in Physiology in April 1893 from St. Bartholomew’s Hospital. In 1895 he was licensed by the Royal College of Physicians (L.R.C.S.), and became a Member of the Royal College of Surgeons (M.R.C.S.).
He became a physician in Spondon, Derbyshire around 1897, and at the time of the 1901 census was living at 42 Oxford Street, Spondon.
In 1908 he joined the 1st North Midland Field Ambulance, R.A.M.C. (T.F.), as a Lieutenant.
On 1st January 1914 he was promoted to the rank of Major. He served on the Western Front with his unit [1st North Midland Field Ambulance] from 26 February 1915, initially as second in command; he commanded the unit from 9th June 1918 until the end of the First World War.
Whilst on leave, on 22nd June 1918, he was decorated with the Distinguished Service Order by King George V at Buckingham Palace.
During the war the 1st North Midland Field Ambulance supported the 46th (North Midland) Division during two particularly notable campaigns - The first day of the Battle of the Somme, 1st July 1916, and during the Battle of St. Quentin Canal from 29th September 1918. On both of these occasions the unit war diary notes his work: At 2am on 1st July 1916, “Major Barron, with 3 medical officers and 60 stretcher bearers, took position at the top of the communication trenches to be able to attend to wounded in the front line trenches, after the battalions left the parapet in their attack at Gommecourt”. 8 days later, on 8th July 1916, he was recommended for immediate reward, to the Assistant Director of Medical Services, on account of his good work on 1st July 1916.
On the 29th/30th September 1918, whilst commanding the 1st North Midland Field Ambulance, he visited all the Advanced Dressing Stations established by his unit, including beyond the St. Quentin Canal, in Bellenglise, to ensure all were adequately resourced. The Canal and Riqueval Bridge had been captured by the 46th Division in an assault crossing on 29th September 1918.
Shortly after the war, on 29th September 1919, he became the Secretary of the first 46th Division annual dinner, held in London. In 1920, when the Territorial Army was formed, he commanded the 137th (North Midland) Field Ambulance and was appointed A.D.M.S. of the 46th (North Midland) Division.
He had gained promotion to the rank of Colonel, and became President of the 46th Division Memorial Committee, arranging a tour to the unveiling of the Memorial, at Bellenglise on 4th October 1922. He was awarded the Territorial Decoration - London Gazette, 4th January 1924.
Due to ill health he resigned his commission in July 1925, and died after a heart operation in Glasgow Royal Infirmary.