Cambodians who survived execution by the Khmer Rouge, forced labor, starvation, and disease crossed the border with Thailand. In Thailand, vulnerable Cambodian refugees died of exhaustion and disease.

　　Cambodians who survived execution by the Khmer Rouge, forced labor, starvation, and disease sometimes crossed the border with Thailand. In Thailand, vulnerable Cambodian refugees died of exhaustion and disease; by November 1979, journalists began to gather at the Thai border. One of them was Arnaud de Wildenberg, a French photographer working for Gamma/Riazon. Most of the Cambodian refugees arrived in Ban Taprik, south of Aranyaprathet, Thailand. The Red Cross selected refugees there and transported them to Sakhao, where a new refugee camp was being built. Many had collapsed in the surrounding forest and could walk no further. In Sakhao, the Khmer Rouge continued to threaten other refugees, often forcing them to accept voluntary repatriation to Khmer Rouge-controlled areas of Cambodia.

 　In mid-1979, the Khmer Rouge still controlled areas of Cambodia. The Vietnamese invasion of Cambodia was imminent. The Khmer Rouge believed that relief efforts along the Thai border would be profitable. The Khmer Rouge hid weapons across the border and posed as innocent refugees. They returned to guerrilla attacks against Vietnamese forces, and on December 25, 1978, the Vietnamese invaded Cambodia and soon occupied most of the country, established a pro-Vietnamese government, and ruled Cambodia, establishing the People's Republic of Cambodia on January 10, 1979. Remnants of the Khmer Rouge retreated to the Cardamom Mountains near the border with Thailand, and other resistance movements erupted in western Cambodia.

　Landmines and booby traps previously set by the Khmer Rouge took a heavy toll on Cambodian refugees. Shortages of food and fresh water added to the refugees' fatigue and illness. The growing toll of the Cambodian tragedy became widely known internationally when Cambodian refugees began pouring into Thailand.

　The devastation of Cambodia began with the Vietnam War, when Vietnamese communists began using Cambodian territory as a base for their guerrilla activities. The U.S. military responded by attacking suspected Cambodian base areas. As the Vietnamese left their strongholds, they became embroiled in fighting with Cambodian government forces. The Vietnamese soon emerged as proxies for the Cambodian rebels. As the fighting escalated, the rebels, the Khmer Rouge, rapidly grew in strength. The besieged Cambodian government surrendered on April 17, 1975.