Cambodia in geomorphology is located between two powers,Thailand and Vietnam. Cambodia historically had been invaded by these two powers numerous times and lost a great deal of territory. It was under French colonial rule for tens of years and its border line was fixed by the French. Even after it was liberated from French colonial rule, it went through political chaos and a brutal massacre committed by Khmer Rouge, that killed more or less two million Cambodians. Khmer Rouge had slaughtered civilians under the pretext of fulfilling the socialist revolution. Vietnam forces had finally driven out Khmer Rouge out of Cambodia and ruled over Cambodia for ten years. But Vietnam had to pull out of Cambodia due to domestic problems and international pressure, forming a pro-Vietnam government in Cambodia, which was called later Hun Sen regime. The government consisted of some Khmer Rouge officers who fled to Vietnam owing to the threat of Pol Pot, the Prime Minister of Khmer Rouge, to kill them and Cambodians residing in Vietnam. After Hun Sen, one of the longest prime ministers in the world, has experienced ups and downs with his political power, he is currently enjoying the political stabilization. In this historical context Cambodians' antagonism toward the Thai and the Vietnamese is obvious and hostility toward the Vietnamese is even more intensified. But Hun Sen regime, which has limitation of its origin formed by Vietnam, has been maintaining a collectively strategic partnership with Vietnam. But relations with Thailand have been strained due to a lot of political conflicts caused by the border disputes. Hun Sen's government capitalized bilateral tensions as tactic of bolstering their political clout and reducing the antagonism of Cambodians toward Vietnam. Chinese ambitions in Southeast Asia may probably force a reassessment of Cambodia's triangular relationship with Vietnam and Thailand. The People's Republic of China has transformed itself from the Hun Sen's bitter foe to its close ally, becoming the largest donor and investor to Cambodia. China continued to increase its influence on Cambodia through what the Cambodian sees as unconditional aid and non-interference in Cambodian internal affairs. Cambodian government has placed top priority on relations with Vietnam, Thailand, and China, including multilateral relations with Western countries. As long as Hun Sen's regime is maintained, relations with Vietnam will last. But China might be a variable.