He was educated at a local elementary school, and in 1908, at 13 years of age, he began working at the Dare Colliery, Cwmparc.
He attended evening classes in economics and history in order to improve his education, and in 1918 he joined the Labour Party.
During the 1926 coalminers' strike Thomas was sentenced to three months imprisonment as the chairman of the Park and Dare Lodge as a result of his involvement in industrial disturbances.
Thomas was a consistent opponent of Welsh nationalism and fought relentlessly against the Parliament for Wales agitation of the 1950s.
He publicly attacked Plaid Cymru on several occasions and in October 1965 he was highly critical of the recommendations of the Hughes-Parry Report on the Legal Status of the Welsh Language.