His first post began in September 1993, as the assistant to Prime Minister Hun Sen until February 1994.

He is a member of the Board of Governors of the Royal School of Administration and the National Bank of Cambodia.

In 2013, he was chosen to succeed outgoing finance minister Keat Chhon and assumed the office on 24 September 2013.

[1] In 2020, he was mentioned as a potential candidate to be prime minister, before the CPP eventually selected Hun Manet in December 2021.

[2] Aun is a graduate of the Moscow State University where he received a Doctor of Philosophy in social and political sciences.