Arthur Thomas was born in 1878 at Liverpool, England. He was working as the manager of a tailoring establishment and living at Toorak when he enlisted with the Australian Imperial Force (AIF) in Melbourne on 8 July 1915. The 37-year-old was allotted the service number 3470 and the rank of private and assigned to the 6th Infantry Battalion. After several months of training Thomas embarked from Melbourne on 11 October 1915 aboard the troopship HMAT Nestor.
After arriving in Egypt, Thomas officially joined the battalion from reinforcements in February 1916. He was promoted to the rank of lance corporal in March and was then sent to the Western Front in France. For the remainder of 1916 the battalion was heavily involved in operations against the German Army, fighting at Pozières and Mouquet Farm and spending winter on the Somme. In February 1917, Thomas was promoted to the rank of corporal and in May of that year was sent to England as a training instructor with the 2nd Training Battalion. He returned to the battalion in early January 1918. In March and April 1918 the battalion helped stop the German spring offensive.
In one of his last diary entries he wrote that it was "very nerve racking to be constantly under shell fire and horrors and dirt and filth, I am sick and tired of the blasted show, it is cruel." A few days later on 8 June 1918, the 40 year old Thomas was killed in action by an artillery shell near Strazeele in France. Arthur Thomas is commemorated on the Villers-Bretonneux Memorial, France.