 Thieme is considered one of the "last great Indologists", advancing all aspects of the philology of Sanskrit, with expertise reaching from the Vedas to the Epics and the Upanishads, Sanskrit poetry and traditional Hindu science (shastra), and Indian grammarians (Panini and his commentators).Thieme was also a comparative linguist, studying Iranian and Indo-European languages in general.Thieme was fluent in Sanskrit, and therefore respected among traditional Indian scholars, holding the inauguration speech at the first World Sanskrit Conference in Delhi in 1971–1972.