[2] Sahala Hamonangan Simatupang began his career at the Meer Uitgebreid Lager Onderwijs (equivalent to junior high school) in Tarutung from 1932 to 1935.

Simatupang was appointed as the assistant to Noermatias, the Inspector for the Post, Telegraph, and Telephone Regions (Pengawasan Daerah Pos dan Telekomunikasi).

[3] A year later, Simatupang was appointed by his party, Perchi, to represent Sumatra in the Central Indonesian National Committee.

[4][5] After the Indonesian National Revolution ended, Simatupang was appointed as the Head of the Post and Telegraph Inspection for the 1st Region, which was based in Jakarta.

[8] On 18 November 1965, Simatupang was named as the assistants for Minister of Land Transportation and Post, Telecommunications and Tourism, Djatikoesoemo.

[11] A year after his office was dissolved, Simatupang was promoted to the post of Secretary General of the Department of Transportation, replacing Muhammad Effendi Saleh.

In an attempt to cure the disease, on 19 August 1992, his family brought Simatupang went to Eindhoven, Netherlands for a coronary artery bypass surgery.