Kampong Cham Province
In Tam was born in Prek Kak village in Stung Treng district, Kampong Cham Province, in eastern Cambodia. As a child he studied Pali at Stung Treng Pagoda, before going on to study at the Lycee Sisowath. After serving as an inspector of the provincial militia, he eventually reached the rank of Brevet-General and rose to the position of governor of Takeo Province.