Later, he lectured at the National Defence College of Thailand and participated in policy formulation Order 66/2523: Communism of Prem Tinsulanonda Government.

Following the Siamese coup d'état of 1947, Prasert joined the Communist Party of Thailand and studied Marxism in China.

He served on the central committee of the Communist Party of Thailand and was a part of the International Peace Conference (1951-1952).

Following his return to Thailand in 1958, he was arrested and accused of being a Communist by the Thanom Kittikachorn and Sarit Thanarat government.

Prasert was the architect of the 66/23 law issued in 1980 which granted amnesty to Communist Party members who gave themselves up to the authorities.