From his resume, Sok Saem was most likely a Vietnamese recruit in 1978

Translated from Khmer by Socheata
Source: http://www.army.gov.kh/index/cvminister/sok_sa_em.html

Army Headquarters

Resumes of Army Infantry Leaders

H.E. General Sok Sa’em
Deputy Army Infantry Commander

• Birth date: 01 April 1956
• Birth place: Chiphou village, Chrork Mtes commune, Svay Teab district, Svay Rieng province
• Current Address: No. 28 Street No. 115, Sangkat Boeung Prolit, Khan 7 January, Phnom Penh
• Education: Former 3rd grade (Junior high school)
• Foreign Language: Vietnamese and English
• Army recruitment date: 03 February 1978
• Combat Duty: Several
• Training: 3 years of army training in Dalat (Vietnam)
• Wife: Chhin Sophan
• Children: 3 (2 sons and 1 daughter)