Professor Thomas is Professor Emeritus of Maritime Law and Founder Director of the Institute of International Shipping and Trade Law, at Swansea University, Wales, UK. Previously he held positions at Cardiff University, the University of East Anglia, UK, and at universities in Europe, Scandinavia, Far East and North America. He was a member of the Departmental Advisory Committee on Arbitration Law which drafted the Arbitration Act 1996, and held the Francqui Chair at the University of Leuven, Belgium, in 2010-2011. He is currently visiting professor at the University of Gothenburg, Sweden, and at the World Maritime University.

He is Editor-in-Chief of the Journal of International Maritime Law, and a member of the editorial board of Shipping & Trade Law. He is a member of the Comite Maritime International (and the International Standing Committee on Marine Insurance), British Maritime Law Association, Chartered Institute of Arbitrators and British Insurance Law Association.

His principal teaching and research interests are in the fields of maritime and shipping law, marine insurance law, international trade law and commercial arbitration.  He has written, edited and contributed to many books and published widely in academic and professional journals. He is editor and contributor to the volumes in the Modern Law of Marine Insurance series.

He is a frequent speaker at conferences and seminars, and also acts as an expert witness and consultant. In 2016 he was made an Honorary Member of the Croatian Maritime Law Association.