Dr. Lao is Head of the Legal Unit of the Center for Social Development, a Cambodian non-governmental organization based in Phnom Penh. Previously, he was successively a Research Fellow at the Institute of Southeast Asian Studies (Singapore), Director of the Institute of Public Administration, Director of the Cambodian Mine Action Center and Director of the Khmer Institute of Democracy.

In addition, Dr. Lao was head of a Cambodian delegation in the negotiations of the repatriation of refugees and the reconstruction of Cambodia at the Paris International Conference on Cambodia in 1989. At the end of the peace process terminating the war in Cambodia he authored a book entitled, The UN Finished Settlement of the Cambodian Conflict.

In addition to his NGO work, Dr. Lao has taught at the Faculty of Law and Economics and at Pannasastra University, Phnom Penh. In addition, he has taught at the University of Toronto in ASEAN and International Studies. Dr. Lao was awarded the Human Rights Watch Honour in 1997 for his work in human rights and the (UNHCR) Nansen Medal in 2000 for his service for fellow refugees, democracy and reconciliation.