Laos, the smallest of the three Communist Indochinese states, must have international help to ward off famine, according to the Laotian government and the U.N. Development Program.

Many of the landlocked nation's 3 million people face starvation in the first few months of 1978 as a result of a drought earlier this year. Failure of rice and other essential crops in some parts of Laos have been as high as 95 per cent, according to a report prepared by the United Nations and the Laotian Agriculture Ministry.

Drought in widespread areas of Southeast Asia has created similar conditions in Vietnam and Cambodia, but only Laos has appealed for international assistance.

"In order to prevent famine conditions arising as a result of the drought," the report said, "it is obvious that advance measures will need to be taken to provide foodstuffs, particularly rice, as well as vegetable oil and sweetened condensed milk."

The government estimated that the crop now being harvested and limited existing stocks could meet its basic needs of until next March.

According to the report, which has been circulated to diplomatic missions in Vientiane, the Laotian capital, the country urgently requires 367,500 tons of food to cover the leanest period from March to November.

A few weeks ago, according to the report, the government decided to seek 122,500 tons of this total in wheat flour from foreign governments and international assistance agencies.

The U.N. unit's office in Vientiane is coordinating the aid appeal. The U.N. Food and Agriculture Organization has reactivated an emergency board it established several years ago to supply relief for Africa's drought-stricken Sahel region.

The FAO has already begun seeking contributions of seeds and pesticides and of help in training Laotian agricultural technicians.

Although the report discusses the potential famine only in terms of the drought, other sources have noted that the convulsions in Laos' economic and social systems since the Communist takeover two years ago had already affected food supplies.

Laos has almost always required some external assistance to keep its population fed. During the years of civil war, the United States pumped in millions of dollars in aid to support the rightist government in Vientiane. When the Communists took over, the U.S. source dried up and the country has been suffering ever since.

Neither Vietnam, which has a close relationship with Laos, nor the Soviet Union, which has established a massive presence in Vientiane, has assumed the U.S. aid role.

Laos' food supply and its overall economic situation have been further complicated by the country's unsteady relations with neighboring Thailand. Until roads linking Laos with Vietnamese ports are completed, the country - and Vientiane in particular - will remain dependent on Thailand for most of its daily diet.

Furthermore, in the rice bowl area of Savannakhet Province in the South, the drought this year was preceded by another, less serious, failure of the rains in 1976. Followed by flooding, this caused crop losses of up to 95 per cent in some parts of the province.

According to the U.N.-Laotian report, total rice output in Savannakhet this year will be around 33,900 tons. In a normal year, the report stated, the province produces 197,400 tons.

A team of U.N. and Agriculture Ministry experts touring Savannakhet and Khammouane provinces in July reported finding fields which were unplowed. "Nor would it be possible for them to be plowed in the immediate future due to the hardness and dryness of the soils," their report stated.