United Nations, N.Y. — Following meetings with President Reagan and Secretary of State George Shultz in New York last month, Cambodia's Prince Norodom Sihanouk says he is pleased that the United States agreed last month to double financial support to anti-Vietnamese resistance groups.
The money - an amount unknown, but believed to be between $6 million and $7 million - is delivered through third parties, he said in an interview. But only China and Singapore supply weapons to help arm Democratic Kampuchea, the tripartite coalition of resistance groups.
Prince Sihanouk also discounted recent Hanoi proposals on Kampuchea (Cambodia) as a clever ploy. Vietnamese Foreign Minister Nguyen Co Thach indicated recently Hanoi's willingness to negotiate with Sihanouk and fellow coalition leader Son Sann, but not with the Khmer Rouge, the third party in the coalition.
Mr. Thach also proposed a meeting with the five big powers, nearly all Southeast Asian nations, and India. He invited UN observers to watch a partial pullout of Hanoi's troops from Kampuchea.
But Sihanouk called this a farce, designed to show ''flexibility'' and an attempt to bring legitimacy on the Heng Samrin regime in Phnom Penh.
''This year's Vietnamese proposals offer nothing new and we must be careful not to fall into this trap,'' he said.
He insists the coalition, which he heads, is gaining ground in fighting the Vietnamese occupiers. But in the long run, Kampuchea remains hostage to Sino-Soviet rivalry. ''If I am to believe what the highest-ranking Chinese have recently told me, a Sino-Soviet reconciliation will never occur,'' he says.
Sihanouk still thinks his own plan for resolving the Kampuchean problem is the most practical and that a coalition should be formed to govern the country and organize free elections. This coalition, he says, should include all four Cambodian political groups: the Khmer Rouge, Son Sann's and Sihanouk's parties, and the Heng Samrin people. (The Khmer Rouge are pro-Chinese, Heng Samrin is pro-Soviet, Son Sann is backed by the middle class, Sihanouk by the peasants.)
''Unfortunately, the Vietnamese want to exclude the Khmer Rouge, and the Chinese will not have anything to do with Heng Samrin and so my perfect square is doomed to remain an imperfect triangle,'' says Sihanouk.
Concerning behind-the-scenes efforts by France, Indonesia, and Japan to bridge the gap between Vietnam and Democratic Kampuchea, he says, ''I wish them well as they are trying to talk sweet reason to Hanoi but I am skeptical.''