New Zealand's Ministry of Foreign Affairs and Trade said it is providing consular assistance to the family of a New Zealander in Cambodia.
For privacy reasons no further information will be provided, it said.
Hazlett was the director of Symmetry Asia, which provides recruitment solutions across Southeast Asia, Hong Kong and Australia.
His online company profile says he had worked in a number of countries since leaving New Zealand in 1996. Hazlett, and his wife and child, have been based in Singapore since early 2011.
A family spokesperson told the Herald a police investigation has uncovered no foul play and Hazlett is expected to have died due to a heart attack.