Serious food shortages in Cambodia are driving inhabitants to this hazardous border region in growing numbers and increasing the pressures on the Phnom Penh government and its guerrilla foes.

The shortages, attributable largely to an erratic monsoon that ruined crops with drought and flooding, have dashed the hopes expressed by some U.N. relief officials only a couple of months ago that Cambodia would be self-sufficient in food production by year's end.

Now, the probability of even more serious food deficits next year is forcing reconsideration of earlier U.N. plans to terminate its emergency relief program for Cambodia at the end of 1981, aid officials say.

Also contributing to the burgeoning border population here have been dissatisfaction with the Vietnamese-installed Cambodian government in Phnom Penh and a Thai voluntary "relocation" program in which Cambodian refugees in camps inside Thailand are being bused to border camps in the hope that they will make their way home.

In the northwestern sector of the border dotted with settlements such as this one, which is controlled by the anticommunist resistance group called the Khmer People's National Liberation Front, the refugee population has increased at the rate of 2,000 a week since the beginning of July and now stands at about 140,000, according to aid officials. Of the new arrivals, they said, a little more than half have fled the Cambodian interior and the rest have come from camps in Thailand.

In addition, more than 60,000 other Cambodians live along the northern part of the border and in the sector south of the Thai town of Aranyaprathet, officials said. The populations of those areas have not grown as much, since the settlements there are controlled mostly by the feared Khmer Rouge. The communist Khmer Rouge were driven from Phnom Penh in January 1979 by Vietnamese invasion troops after nearly four years of brutal rule.

The biggest growth has been at this camp, which straddles the border about 15 miles north of Aranyaprathet. In the past five months, its population has risen from about 17,000 to nearly 40,000.

Although such growth bolsters the base of support and potential recruitment of the Khmer People's National Liberation Front, front officials say the influx is more a burden than a boon.

Besides, they said, the front is unable to expand its military force without new arms shipments. It currently claims to have grown to 9,000 troops, thanks to Chinese weapons delivered earlier this year.

However, according to a Western doctor on the border, "Refugees say the situation in Cambodia is getting worse." As a result, he said, Cambodians keep showing up at the border looking for food from relief agencies. Most of the casualties his hospital now receives, he said, are civilians who step on land mines while searching for food or building materials.

According to relief officials and diplomats in Bangkok, the most severe food shortages have developed in eastern Cambodia.

Drought and floods have ravaged half a dozen provinces, and the country's 12 most populous provinces may well have food deficits, one Western diplomat said. It amounts to a serious setback in Cambodia's recovery from the famine of 1979.

Although estimates of the shortages vary, all projections of Cambodian food production are much bleaker than a few months ago.

The U.N. Food and Agriculture Organization estimates a deficit of 160,000 tons of food, mostly rice, when the current rainy season's crop is harvested at the end of the year.

According to a well-informed foreign source, the Phnom Penh government projects a deficit of 450,000 tons for all of 1982. This corresponds roughly with Soviet estimates, which put the deficit at 400,000 to 500,000 tons for next year. An Eastern European assessment, meanwhile, forecasts a deficit amounting to 40 percent of Cambodia's minimum food requirements.

The total 1981 deficit, defined as the difference between the food requirements and domestic production, comes to about 220,000 tons, officials said.

According to a relief official with broad experience in Cambodia, the gravest food problems are in southeastern Cambodia, where the worst drought and floods have struck, sometimes only a few miles apart.

Because of the seriousness of the problem, Western aid donors are reassessing the previous plan to declare the Cambodian emergency over and stop the U.N. special relief effort at the end of the year. According to aid officials, an extension of the program now appears likely.

A donors' conference was held in New York Sept. 10, and further meetings are planned after an independent survey of the Cambodian food situation.

A U.S. official said Washington "has no problem in extending the aid" as long as the need for it can be justified. However, as Soviet aid pledges have been steadily declining, roughly 20 percent of this year's deficit will remain uncovered by foreign aid or existing stocks, relief officials said. percent of Cambodia's minimum food requirements.

The total 1981 deficit, defined as the difference between the food requirements and domestic production, comes to about 220,000 tons, officials said.

According to a relief official with broad experience in Cambodia, the gravest food problems are in southeastern Cambodia, where the worst drought and floods have struck, sometimes only a few miles apart.

Because of the seriousness of the problem, Western aid donors are reassessing the previous plan to declare the Cambodian emergency over and stop the U.N. special relief effort at the end of the year. According to aid officials, an extension of the program now appears likely.

A donors' conference was held in New York Sept. 10, and further meetings are planned after an independent survey of the Cambodian food situation.

A U.S. official said Washington "has no problem in extending the aid" as long as the need for it can be justified. However, as Soviet aid pledges have been steadily declining, roughly 20 percent of this year's deficit will remain uncovered by foreign aid or existing stocks, relief officials said.