Arthur Thomas was born in Cardiff on 16 September 1891. He was the son of William Thomas, a labourer in the local shipyards who was originally from Bristol and his wife, Sarah, who was a native of Cardiff. He had one younger sister named Mary. The family, along with William's father, Edwin, a widower originally from Pill, Somerset, and also a labourer in the docks, lived at 12 Forrest Street, Grangetown, Cardiff. Arthur had worked as a grocer's warehouseman, but by the time he enlisted in the newly formed Cardiff City Battalion of the Welsh Regiment he was employed as a conductor on the city's tram system. He died, aged 24, of wounds received during the first attack on Mametz Wood on 7 July 1916 and is commemorated on the Thiepval Memorial to the missing of the Somme who have no known graves.