Eng Chhai Eang was an outstanding student, was honored and was the top number one in the National Mathematics competition in 1987.

From August 1999 to December 2005, and then again from September 2007 to January 2009, he held the position of Secretary General of the Sam Rainsy Party.

From April 2013 to March 2017, Chhai Eang served as the Vice Chair of the Steering Committee of the Cambodia National Rescue Party (CNRP).

In September 2014, Chhai Eang was elected as the Chairperson of the First Commission on Human Rights, Complaints, and Investigations of the National Assembly.

Following the dissolution of the CNRP in November 2017, Chhai Eang was banned from politics, and left Cambodia.