A professional soldier, General Kriangsak fought in the Korean War as well as in Vietnam. In 1977, while the Supreme Commander of the Thai army, he staged a successful coup against prime minister Thanin Kraivixien.
General Kriangsak is widely credited for quelling a long-running Communist insurgency in northern Thailand. Reportedly, he allowed the Chinese to ship arms to the rebel Khmer Rouge in Cambodia in exchange for China withdrawing its support of the rebels, although this is denied by the Thai government, which cities his offer of amnesty as the primary reason.
General Kriangsak voluntarily retired in February 1980 and was succeeded by General Prem Tinsulanonda.