Tou Samouth (Khmer: ទូ សាមុត; c. 1915 – 20 July 1962), also known as Achar Sok (អាចារ្យសុក), was a Cambodian politician. One of the two founding members of the Kampuchean People's Revolutionary Party (KPRP), the other being Son Ngoc Minh, and head of its more moderate faction. He is mainly remembered for mentoring Saloth Sar, who would later change his name to Pol Pot.

Samouth was a Khmer Krom who was born and raised in Cochinchina (in the Southern part of Vietnam).^[2] Samouth was trained as a Buddhist monk in his youth, and by World War II, he was professor of Pali at Unnalom Monastery in Phnom Penh. In 1945, an American air raid directed against Japanese military targets struck the Monastery, causing several deaths. Samouth was so frightened by this event that he fled to the countryside, eventually making his way to Vietnam, where he joined the Viet Minh.^[3] In the late 1940s, Samouth lectured groups of Khmer recruits on political awareness and economics.

Samouth went on to be a founder member of the Khmer People's Revolutionary Party, the precursor to the Communist Party of Kampuchea, along with Son Ngoc Minh. He was also one of the leaders of the United Issarak Front, a broadly leftist affiliation of various disparate elements of the anti-French resistance, the Khmer Issarak. When the Front formed its 'Khmer Resistance Government', Samouth was named as the Interior Minister.

As head of the Vietnamese-sponsored 'urban' faction of the Cambodian Party, Samouth's presence helped to attract many Buddhist monks to the left-wing cause. The 'urban' communists, as opposed to Sieu Heng's 'rural' cadres, advocated generally more moderate policies; in particular, they supported the presence of the Cambodian king, Norodom Sihanouk, as a figure of national unity and a useful ally in the North Vietnamese attempt to overcome the South. It was within Samouth's faction of the Party that Pol Pot, and the other recent returnees from Paris who would form the nucleus of the Party's later incarnation as the Khmer Rouge, would gain experience. Samouth appears to have adopted Pol Pot as his protégé, leading to the latter's rapid promotion within the Party subsequent to Cambodian independence according to 1954 Geneva Accords.

The 'rural' cadres of the party were decimated by Sihanouk's security forces in 1959, following Sieu Heng's defection to the government. In the face of increasing repression from Sihanouk's government, the KPRP held a secret meeting in 1960 in Phnom Penh railway station. Samouth, who still advocated cooperation with Sihanouk, was elected General Secretary. Pol Pot was named as third in the Party's hierarchy behind Samouth and Nuon Chea.^[4]

Samouth disappeared in disputed circumstances in July 1962; the event was a closely guarded secret until the later 1970s. Although he is usually assumed to have been murdered by Sihanouk's police, it has been suggested that Pol Pot may have arranged Samouth's death to ensure his own promotion to party secretary. The historian Ben Kiernan claims that there is strong evidence that Pol Pot's circle was responsible for Samouth's disappearance: in particular a secret Party report on 'internal enemies', dating from 1978, accused Kandal Province Secretary Som Chea of killing Samouth. Chea, who was later executed, had been a courier for Pol Pot's group in 1962.^[5] Pol Pot denied these claims in one of the last interviews before his death, stating that Samouth, who had left his safe house to obtain medicine for his sick child, had been arrested by Lon Nol's men, interrogated, and killed: "If Tou Samouth had talked, I would have been arrested. He was killed at Stung Mean Chey pagoda. We loved each other."^[6]

Pol Pot was elected Party secretary early in 1963, and subsequently broke decisively with the Vietnamese communists, securing instead the backing of China.

One of the main streets of Phnom Penh was named in honour of him after his death, until it was changed to Norodom Boulevard in 1997.

• Chandler, David P., Brother Number One: A political biography of Pol Pot, Westview Press, 1992, ISBN 0813309271
• Kiernan, B. How Pol Pot Came to Power. London: Verso, 1985