From In Buddha’s Company: Thai Soldiers in the Vietnam War, by Richard A. Ruth (U. Hawaii Press, 2011), pp. 188-189:
The Thai soldiers saw South Vietnam as a separate country in a conception that differed from their understanding of their immediate neighbors Laos and Cambodia. Many of these soldiers had passed through those two countries in their youth. Private First Class Aran’s childhood home in Nong Khai, for instance, was within sight of the Mekong River and the banks of Laos opposite. As he recalled, “It was like going into my sibling country. Back then Thailand and Laos weren’t that different from each other. There was no ideology [separating them] at all. We crossed over to play like normal. We could eat and sleep, and then cross back. [The Lao people] were like our relatives; we could go back and forth [between Thailand and Laos] all the time.” Those soldiers from the southern Isan subregion, many of them from districts where Khmer was spoken as a first language, enjoyed similar ease in crossing the Thai-Cambodian border in the period before the World Court awarded full ownership of Prasat Khao Phra Wihan (Preah Vihear in Khmer) to Phnom Penh in 1962. For the ethnic Khmer living in southern Isan’s Sisaket, Surin, and Buriram provinces, a jaunt into Cambodia was as unremarkable as the boat ride on the Mekong River made by their ethnic Lao counterparts in the north.
Vietnam was different. Its cultural dissimilarities more so than its geographic distance put it into a separate category. It seemed Chinese. The strong cultural similarities between the Vietnamese and the Chinese made such comparisons inevitable. The historical Vietnamese embrace of Confucian principles, Mahayana Buddhism, Chinese script (as well as Nom, the Vietnamese indigenous script that resembles Chinese to many outsiders), and the classics of Chinese literature encouraged the Thais to see Vietnam as belonging to China’s sphere. It seemed distant beyond the kilometers that separated it from Thailand.
Upon their arrival in Vietnam, the first action undertaken by many Thai volunteers was to acknowledge the presence and sovereignty of the local spiritual regime. As soon as Sergeant Khamron set foot in South Vietnam, he dropped to his knees, scooped up a handful of dirt, and sprinkled it over his head. He carried out this impromptu gesture to ensure that Mae Thorani would protect him while he was in South Vietnam…. “If you are Buddhist, they train you to do things like this,” he explained. “There is a khata [verse] that says, ‘When you go to a foreign land/Entrust your care to Mother Earth.’ It is the same thing when you return. When I got back [to Thailand], I immediately knelt down, took up some dirt, and sprinkled it on my head. I said, ‘I’m back.'” Khamron’s decision to carry out the same action on returning to his homeland underscores the degree to which many soldiers saw South Vietnam’s spiritual forces as belonging to a separate (and specifically Vietnamese) realm. Despite sharing the same physical landmass and duplicating the same flora, fauna, and weather, the two countries were seen to harbor individual and esoteric spiritual actors. The sovereignty of each area belonged to local spirits. For this reason, some Thai soldiers brought their own soil with them. They collected samples of dirt, which they addressed as “Mae Thorani,” and carried the samples with them to South Vietnam.