[5] Thomas returned to the University of Guyana as a professor and served as director of the Institute for Development Studies, created in 1973 as a department within the Faculty of Social Sciences.
[6] Thomas was elected chair of the University of Guyana Staff Association, and acted in an advisory role for other non-government organizations that campaigned for democracy and social justice.
[5] In 1974, Thomas helped Walter Rodney in building the Working People's Alliance (WPA)[7] as a reaction to the political landscape that had been divided by ethnicity.
Strife between Afro-Guyanese and Indo-Guyanese was historically encouraged as a form of labour control for the benefit of plantation owners, and at the time also a strategy for the Forbes Burnham administration to maintain political power.
[13] Thomas was co-ordinator of the Regional Programme of Monetary Studies, a member of the Commonwealth Group of Experts on the Changing World Economy and North-South Relations (1990-1991) and the UNDP Group of Experts on Designing the Future: South-South Cooperation in Science and Technology, 2000 and served as a member of the WHO/PAHO Advisory Committee on Health Research, 1996–1999, and was appointed in 2002 to the United Nations Secretary-General's Millennium Project Task Force to monitor the implementation of the Millennium Development Goals.