He completed his education in the Leiden University with the title Meester in de Rechten (Bachelor of Law).

While in the Rechts Hogeschool, his professors disliked Assat's political activities and Assaat failed his exams.

He then joined the Indonesia Party (Partindo) with Adnan Kapau Gani, Adam Malik, and Amir Sjarifuddin.

[2] During his time as an influential figure in Indonesian politics Assaat became known for his extremist views against the ethnic Chinese minority of Indonesia.

During the late 1950s, Assaat began to openly criticize Sukarno before moving to his home island of Sumatera to join a short-lived, CIA-backed rebellion of junior officers of the Indonesian army which had called itself the Revolutionary Government of the Republic of Indonesia.