Ms. Thomas was admitted to the bar in California in 1973, in Paris, France, in 1992, and in New York in 2001.  After receiving a B.A. from Wellesley College in 1969 and a J.D. from Stanford Law School in 1972 she taught briefly at Stanford Law School and worked for the federal government in Washington, D.C. before becoming associated in 1979 with the firm of Surrey & Morse, a law firm based in Washington, D.C. that specialized in international transactions. Among other issues, she worked on the initial stages of an early landmark international arbitration, Northrop v. Triad, which concerned a United States corporation’s payment of fees to an agent to procure a defense contract from Saudi Arabia.

In 1981 she was invited by the Government of China to be a consultant to the Ministry of Foreign Economics and Trade (MOFERT) and to be the visiting professor of international commercial law in the Law School of the Beijing Institute of Foreign Trade (now the University of International Business and Economics (UIBE) in Beijing), run under the auspices of MOFERT, where she stayed from 1982-1985. While in China, in addition to teaching at the University, she advised MOFERT on the development of new commercial laws, and both prepared the materials for and supervised an advanced training course for MOFERT officials in such subjects as international commercial law, international trade law, international finance and international dispute resolution.  Contributors of material for this training course included the United States Department of Commerce, the office of the United States Trade Representative, Merrill Lynch, IBM and a number of other corporations and government agencies.

In 1985 she was invited to be a Senior Fellow at the Lauterpacht Research Centre for International Law at Cambridge University, England, where she specialized in comparative and international law and the resolution of international disputes involving sovereign states.  She later became a consultant to the ICC Institute, ICC Court of Arbitration, Paris, France, and worked on the development of norms for the procurement and use of evidence in international commercial arbitrations. For nearly eight years she worked in Paris in collaboration with both French and international firms on disputes before international tribunals concentrating on disputes that involved both common law and civil law legal concepts and procedures.  In 1992 she became a member of the Paris bar, licensed to practice law in France.

In 1994 Ms. Thomas became one of the highest ranked civilians and the commission member responsible for legal matters on the United Nations Commission for Western Sahara (MINURSO) a UN peacekeeping mission appointed to conduct a referendum for self determination for the indigenous population of Western Sahara in North Africa. Since leaving that position she has advocated for the right of the people of Western Sahara to self determination under international law.

She is currently in private practice in New York.