evidence: In the 1960s the brilliant jurist and nationalist Khmer student Sarin Chhak wrote a political science doctoral dissertation in Paris, focusing on the borders between Cambodia and Laos and South Vietnam. His thesis was later published as a book.Footnote 66 Chhak argued not only that Stung Treng should be part of Cambodia, but also parts of present-day Laos, such as Attapeu, and from Vat Phou in Champasak south, since ruins there indicated that Khmers once inhabited areas north of the present Laos–Cambodia border. He emphasised that the territories that were previously occupied by Khmers, including the Pakse region (in present-day Laos), and areas lost to Vietnam, including Dak Lak Province, and areas of the Song Be, Tay Ninh, Go Dau Ha and Ha Tien further south should belong to Cambodia. Later he became Cambodia's Ambassador in Egypt, and in 1970 he became Foreign Minister for the Royal Government for the National Unification of Kampuchea (GRUNK), the pro-Sihanouk government in-exile established by a broad coalition of leftists and neutralists, based in Beijing, China.Footnote 67 He remained Foreign Minister for a short period even after Cambodia came under the full control of the Khmer Rouge in 1975, but without any real power.