Thomas was born in Merthyr Tydfil to a family who were active in the Independent Labour Party (ILP).
[1] He studied teaching at Borough Road College and then worked as a schoolteacher in Merthyr, Pontypridd, and later Willesden and Kingsbury in London, eventually becoming acting head at the Woodfield Day Special School, before retiring in 1965.
[2] Thomas was a member of the ILP from an early age, and by the late 1930s was the representative for South Wales on its National Administrative Committee.
[3] The ILP disaffiliated from the Labour Party in 1932, and Thomas was a member of a panel who considered the possibility of reaffiliation, in 1939.
Thomas continued to serve on its national committee until 1984, when he stood down due to difficulties with his eyesight.