Thas received in 1969 his Doctor of Philosophy from Ghent University under Julien Bilo with thesis Een studie betreffende de projective rechte over de totale matrix algebra der 3x3-matrices met elementen in een algebraïsch afgesloten veld K. He is an emeritus professor at Ghent University.
In 1994 Thas received the Euler medal. In 1998 he was an invited speaker at the International Congress of Mathematicians in Berlin with lecture Finite geometries, varieties and codes. He received in 1969 the prize of the Royal Academy of Sciences, Letters and Fine Arts of Belgium, in 1970 the Scientific Louis Empain Award and in the same year the François Deruyts prize of the Royal Academy of Belgium. In 1988 he became a member of the Royal Flemish Academy of Belgium for Science and the Arts. He was vice-director of the Class of Sciences in 1998 and director in 1999. In 1999 he was awarded an Erskine Fellowship of the University of Canterbury, New Zealand, in 2008 he was Platinum Jubilee Lecturer at the Indian Statistical Institute, and in 2012 he became one of the inaugural fellows of the American Mathematical Society.
With Koen Thas, H. Van Maldeghem Translation generalized quadrangles, World Scientific 2006with Stanley E. Payne Finite generalized quadrangles, Pitman 1984, 2nd edition, European Mathematical Society 2009with J. W. P. Hirschfeld General Galois Geometries, Oxford University Press 1991Projective geometry over a finite field and Generalized Polygons in F. Buekenhout Handbook of incidence geometry, North Holland 1995with J. Bilo Enkele aspecten van de theorie der axiomatische projectieve vlakken, Simon Stevin, Supplement, Vol. 55, 1981(For a complete list of papers see Homepage in Ghent).
In 1988 he became a member of the Royal Flemish Academy of Belgium for Science and the Arts. He was vice-director of the Class of Sciences in 1998 and director in 1999.
