In spite of Soviet efforts to develop closer ties with Cambodia and promises of large-scale assistance, Moscow's food aid to that destitute country last year amounted to less than half the original target, according to Western diplomats and relief officials here.

Moreover, the officials say, the Soviets now require the Cambodians to pay for some of the food shipments with rubber exports from plantations developed with Soviet help. In addition, the officials believe, a significant portion of Moscow's purported humanitarian aid goes to Vietnamese occupation troops deployed in the country.

The Soviet role in international relief efforts in Cambodia is expected to come under scrutiny next month when Western aid donors meet in New York to consider new aid proposals for 1982. A U.N. emergency relief program for the Cambodian interior had been scheduled to end on Dec. 31, but a disastrous rice harvest last fall led to predictions of serious shortages in 1982 and prompted U.N. agency appeals for continued aid.

At their last meeting, in November, the Western donor nations approved continued assistance worth $16 million for the Thai-Cambodian border area in 1982. But they demanded further U.N. assessments of the situation in the interior before deciding on additional aid at their next meeting, scheduled for Feb. 4.

That decision will depend largely on a report by the United Nations' World Food Program. According to U.N. officials here, a World Food Program team is currently assembling in the Cambodian capital, Phnom Penh, to carry out a two-week assessment of food needs and aid distribution.

The question of aid to Cambodia is a complicated one because the communist government in Phnom Penh is not recognized by any Western nation and does not control some parts of the country.

Southeast Asia's noncommunist nations and Western countries have insisted on separate aid for the border area to feed Cambodian followers of resistance groups battling the Vietnamese occupation forces.

If the Western countries approve new relief for the Cambodian interior administered by the Phnom Penh government, U.N. officials here said, the donors are expected to insist on major changes in the aid program. Instead of a scattershot approach designed to spread the aid around as broadly and quickly as possible, any new program will target specific needs and require more monitoring of how the supplies are used, U.N. officials said.

"Initially we found the whole place in a hopeless situation, so it made sense to pour it in," one senior official said of the original U.N. relief program to counter Cambodia's 1979 famine. "Now it's less severe and we have to pinpoint the needs."

Accordingly, proposals have been drawn up to channel food aid to malnourished children, orphans, widows, lactating mothers and other needy groups in six provinces especially hard hit by crop failures caused by last year's erratic monsoon. The proposals also provide for procedures to ensure that deliveries are not diverted to the military.

The United States has been in the forefront of countries insisting on such changes and has expressed willingness to support new aid for the Cambodian interior if they are implemented, diplomats said. However, they said, members of the European Community have indicated skepticism about the need for continued relief aid.

A senior U.N. official here expressed optimism that the donors would "come across for purely humanitarian reasons" and because a failure to do so might cause more Cambodians to drift toward the western border and increase pressure on Thailand.

Besides assessing food needs, the World Food Program mission to Phnom Penh will also look into whether requirements can be met by "bilateral donors," in other words the Soviet Bloc, a Western diplomat said.

Judging by Moscow's record in 1981, this would appear unlikely, officials said.

"The Russians have reneged on a significant part of the aid they promised," a Western diplomat said.

"The indications are they're cheapskates," said another.

At the beginning of last year, the Soviets said they would supply about 100,000 metric tons of food aid to Cambodia during 1981, down from the roughly 150,000 tons Moscow provided the year before, well-informed officials said. In subsequent months, they said, Moscow whittled down this target to 80,000 metric tons, then later in the year to 55,000 tons.

By the end of 1981, however, actual Soviet deliveries amounted to only about 45,000 tons, the officials said. Of this amount, only a bit more than half was made up of the most needed commodity, rice.

About 20,000 tons was Soviet wheat flour, which is consumed in cities but rarely in the countryside where the greatest needs are.

By contrast, 1981 food aid to Cambodia provided by the Western donors through the World Food Program came to more than 80,000 metric tons--including 15,000 tons pledged in 1980--and all of it was rice, officials said.

This year the food deficiency could be even more serious than in 1981. Whereas Cambodia's 1981 rice deficit totaled about 63,000 metric tons, the Rome-based Food and Agriculture Organization estimates a shortfall this year of nearly 280,000 tons.

In a report issued in November, the organization proposed that the Western donors and the Soviet Bloc each provide 100,000 tons of rice and that the Cambodians themselves make up the rest of the deficit by substituting other foods. This aid would cost each group of donors roughly $50 million, excluding spare truck parts, fuel and other items needed to distribute it, a U.N. official said. Western aid alone last year totaled $100 million for the interior and $88 million for the border feeding program, refugee holding centers and affected Thai villages.

The FAO's ideas on making up this year's food deficit seem unlikely to be met with much enthusiasm by Cambodian officials, some of whom are reportedly annoyed with the poor Soviet performance last year.

In addition, Western aid officials are gnawed by the suspicion that much of the Soviet food assistance is diverted to support the Vietnamese war effort against the resistance groups, chief among them the ousted Khmer Rouge regime that ruled Cambodia from 1975 to 1979.

Relief officials in Phnom Penh reportedly have not seen any sign of Soviet food aid in visits to villages, but only in warehouses at the Soviet-run port of Kompong Som.

"I suspect it goes to the Vietnamese in Cambodia and the Vietnamese in Vietnam," one well-informed official here said. "It's strange to have such huge food shipments and you can't find a single bag of it in the countryside."