During his early career as a scientist, he developed an interest in communicating scientific ideas to adult audiences. He was able to carry this concept to fruition as the Director of Adult Programs in the Sciences at the University of Wales at Swansea where he introduced a wide range of programs in mathematics, physics, and associated sciences into the adult curriculum. These programs were developed and subsequently emulated by other universities in the United Kingdom.

In 1978, he became the Deputy Director of the Department for External Studies at the University of Oxford, where he assumed responsibility for all the adult education provision of the University. In 1986 he became Acting Director of the Department and oversaw the rapid expansion of the Department's offerings and the introduction of credit and professional programs. He became the Director in 1989. In 1990 Oxford established a new college for adult students, of which Dr. Thomas was named the Founding President. The inception of the new college, together with his continuing work in the department (renamed Department for Continuing Education in 1990) marked a major progression in Oxford's university outreach and adult education.

Dr. Thomas is the author of numerous books and professional articles in his field and has lectured widely in Europe, the United States, and Japan. As a Visiting Professor and Scholar to a number of universities (including Harvard, University of California-Berkeley, University of Washington, University of Georgia, and the Smithsonian Institution) he continued to expand continuing education internationally. He is a member of the Higher Education Funding Council for Wales, the Executive of the Universities Association for Continuing Education, and many other bodies in the field of continuing higher education.