Barend Jan (Baas) Terwiel (born 24 November 1941) is a Dutch-Australian anthropologist, historian and Thai studies scholar.

He has written books on ethnology of Tai peoples and Ahom, the history and culture of Thailand as well as historical travel of Europeans to mainland Southeast Asia.

After his military service in Netherlands New Guinea, Terwiel had to spend a few days in Bangkok due to a lack of transport capacity, which aroused his interest for Thailand.

For his doctoral studies, he moved to the Australian National University where he graduated with a Ph.D. in 1972.

[3] For his dissertation project, he had himself ordained as a Buddhist monk and lived for a year in a village monastery in central Thailand to explore ceremonies and religious practice of Thai Buddhism from an inner perspective.

[1] From 1972 to 1974 Terwiel worked as a coordinator training volunteers at the Dutch Royal Tropical Institute, Amsterdam.

In the same year, he was appointed Professor at the Institute of Ethnology of the Ludwig Maximilian University of Munich, Germany.

In 1992, Terwiel moved to the Asia and Africa Institute of the University of Hamburg where he held the Chair of Languages and Cultures of Thailand and Laos until his retirement in 2007.

Seven probes in rural South East Asia : socio-economic and anthropological.

Thon Tai (dōēm) mai dai yū thīnī.

Tai Ahoms and the stars : three ritual texts to ward off danger = Tamrā dūangdāo Thai ʻĀhom : ʻēkkasān sado̜ khro̜ 3 samnūan.

Monks and magic : an analysis of religious ceremonies in central Thailand (3rd rev.

A traveler in Siam in the year 1655 : extracts from the journal of Gijsbert Heeck.

Monks and magic revisiting a classic study of religious ceremonies in Thailand (New ed).

Tai Ahoms and the Stars : Three Ritual Texts to Ward off Danger.