Henley is interested in the politics, history, geography and sociology of Southeast Asia, particularly Indonesia. He has published, among other subjects, on nationalism, regionalism and ethnicity, political institutions and ideology, and comparative economic histories of Southeast Asia. Aside from his position as professor, he is a member of the Scientific Committee of the Royal Netherlands Institute for Southeast Asian and Caribbean Studies (KITLV) and the Advisory Committee of the Van Vollenhoven Institute for Law Governance and Society.

Previously, he worked as Southeast Asia coordinator for an international research project in which he compared development policy and performance in Southeast Asia and Sub-Saharan Africa.

Henley graduated from Cambridge University and earned a PhD at the Australian National University. He has been a lecturer at Griffith University in Brisbane. Furthermore, he worked as researcher at the KITLV in Leiden, and as research fellow at the Asia Research Institute of the National University of Singapore.