Pash was born as Avtar Singh Sandhu in 1950 in a small village called Talwandi Salem in Jalandhar district of Punjab, in a middle-class farmers family. His father Sohan Singh Sandhu was a soldier in the Indian army who also composed poetry as a hobby. Pash grew up in the midst of the Naxalite movement, a revolutionary movement waged in Punjab against the landlords, industrialists, traders, etc. who control the means of production. This was in the midst of the Green revolution which had addressed India's problem of famine using high yield crops, but had also unconsciously led to other forms of inequities in Punjab.

In 1970, he published his first book of revolutionary poems, Loh-Katha (Iron Tale), at the age of 18. His militant and provocative tone raised the ire of the establishment and a murder charge was brought against him. He spent nearly two years in jail, before being finally acquitted. In 1972, the 22-year-old started a On acquittal, he became involved in Punjab's Maoist front, editing a literary magazine, Siarh (The Plow Line). He became a popular political figure on the left during this period and was awarded a fellowship at the Punjabi Academy of Letters in 1985. He toured the United Kingdom and the United States the following year; while in the U.S., he became involved with the Anti-47 Front, opposing Sikh extremist violence. His words had a great influence on the minds of the people.