Some of the largest communities in northern Thailand are refugee camps, and they are growing each month.

Since the beginning of 1978, the number of refugees here has risen about 50 percent. Despite efforts to resettle them in the United States, France and other countries, only one refugee leaves the camps for every three who arrive. By the end of this year 200,000 people, almost all fleeing from Laos, are likely to be in camps -- as many people as the United States has accepted since its Indochina wars ended four years ago.

The war in Laos was always a sideshow to the fighting in Vietnam and the Lao refugees have remained at the periphery of world attention caught by the dramatic flight of Vietnamese boat people and Khmers fleeing atrocities in Cambodia.

No television cameras are watching the Mekong River as the thousands of Lao and hill trbesmen -- known as Meo when they formed the CIA's secret army in Laos, but who call themselves Hmong, or Free People -- make their way to camps along the Lao-Thai border.

They arrive here, where 38,000 are gathered; at Ubon, where there are another 38,000; at Loei, 15,200; at Ban Nam Yao, 13,200, and at four other places near the border.

For some of the refugees, particularly Lao from the capital, Vientiane, escape is not difficult. Patrols are lax. Boatmen can be paid to cross the Mekong. But for most Hmong, against whom the Communist government is carrying on a campaign, there is a long and difficult walk followed by a likely encounter with Communist troops on the riverbank.

For the elderly and the very young the trip can be impossible. Those families with too many weak members. refugees here say, are trapped in the Lao mountains, unable to get away.

Va Her, 25, a former lieutenant in the Hmong army, walked 15 days with 79 people from Laos' tallest mountain, Phu Bia, to the river. His wife strapped their 2-year-old daughter on her back and they floated into the Mekong holding onto bamboo poles.

His wife's pole spun in the current, turning her onto her back and forcing her briefly underwater. The daughter drowned.

Va Her and his wife made their way back to the Laos side of the river to bury their child while the rest of their group crossed to Thailand. On March 18, the young man -- who fought with the Americans, surrendered to the Communist Pathet Lao at the CIA's once-secret Long Cheng head-quarters in 1975, and then escaped a reeducation camp two years later to fight with Hmong guerrillas near Phu Bia -- crossed the river and became a refugee.

Mao Thao and her family were driven out of their village by government troops in December. In January, she gave birth to a son. She was undernourished and had little milk and there was almost no food in the jungle. For 27 days, her group walked through the hills to Thailand and arrived March 18.

Her son is 2 months old and weighs a little more than 4 pounds. His skin is stretched tight over his bones. He lies almost motionless with half-closed eyes in his hospital bed, wrapped in a cloth despite the heat in which others sweat.

These new arrivals will be in refugee camps for a long time. Many of the Lao and Hmong who came in the first refugee wave in 1975 are still here. People must wait more than a year before they are even interviewed by U.S. immigration officer because there already is a long list of refugees qualified for resettlement in the United States -- if the United States had places for them.

About 17,000 refugees who fled by land will be approved to go to the United States in the current refugee year ending April 30.

The Carter administration and Congress are considering a program for the future with indications it will permit a faster flow of people from camps into the United States. But it would take an enormous increase to keep up with new arrivals, let alone reduce the refugee population.

At the beginning of March, 145,824 refugees were living in Thailand -- 125,320 from Laos, 14,974 from Cambodia and 5,530 from Vietnam. About 4,000 have been arriving each month, although more than 7,500 came in January and 12,293 reached Thailand in the first two months of the year.

In Malaysia, where most of the Vietnamese boat people have sought refuge, there are more than 50,000 refugees.

Only France, Australia and Canada in addition to the United States have accepted large numbers of refugees. About 40,000 have gone to France, 13,000 to Australia, 6,000 to Canada and 5,000 to all other countries combined.

Officials of the U.N. High Commissioner on Refugees who care for the refugees in the camps say that psychological problems of prolonged camp life are worst among refugees from Laos.

About 40 percent have been in camps for more than three years. One in three are children under 12.

The camps have become communities, with refugee leaders, and refugees can get day passes to visit nearby Thai towns. Here, there is even a telephone link to Vientiane. Some refugees use it to keep in touch with their families across the river.

But camp life is frustrating and boring. For months and years people eat, sleep and have little else to do except talk about the future -- and the past.

For the Hmong, the problem is particularly acute. The same attachment to their mountain homes and hatred for communism -- and the Vietnamese who increasingly dominate Laos -- which made them eager recruits for the secret war begun in the early 1960s, makes many reluctant to leave the camps even if they qualify for resettlement.

Many of the men whose whole lives have been warfare speak of wanting to fight again if the Hmong could find a new supplier of arms and ammunition. They know that "Mr. Tony," "Mr. Jim," "Digger" and the other advisers who trained and paid them are not coming back. But their determination to continue their struggle is enough to make a covert action man's palms itch.

Many talk of China as the new ally for the Hmong and see no reason why Chinese, despite their communism, would not be acceptable.

There were about 350,000 Hmong in Laos in the 1960s. Now so many have been killed or fled there may be only 100,000. In China, there are several million, and the Chinese-Vietnamese confrontation makes them likely soldiers for a new round of fighting or border harassment.

The Hmong resistance, which has been going on unaided for four years, seems close to defeat. Ning Chao Xiong, a former officer with Meo general Vang Pao, commanded 60 armed men in the mountains after the Vang Pao surrender. When they began, each man had between 100 and 200 rounds of ammunition. By mid-1978, there was no more ammunition and he led a group of 26 people, including six men with rifles, to Thai-land.

As happened to so many Hmong groups, they encountered a Communist patrol as they crossed the Mekong at the end of their 34-day march. In Xiong's group, only one man was killed.

Nhia Gao Vue came with a group of 94. A patrol intercepted them at the Mekong and 36 were killed, he said in an interview. His men had nine rifles left and a few rounds of ammunition, which they surrendered to That police.

Vue and Xiong are among the Hmong who would like to resume fighting and are therefore reluctant to travel too far from their homeland in case a new patron makes continued warfare possible.

The recent arrivals in Thailand describe their last year grimly. Not only were they short of ammunition, but most had trouble finding food as they kept on the move to avoid enemy attack.

Rockets, napalm, artillery and mortars were used against them, they say. In addition to rockets, enemy planes sometimes dropped chemicals on the Hmong, according to dozens of refugees.

No one is certain what the chemicals were. Hmong who watched various attacks describe a mist which some say was white, some call yellow, some red and others mixed colors.

Xiong said 500 persons in one area where he was living died from one chemical attack. The chemicals caused dizzyness, headaches, vomiting and diarrhea, Hmong witnesses say.

What is clear from each new refugee's account is that large numbers of Hmong have died and that conditions for those who remain in Laos are desperate.

Vang Pao and an elite slice of his men and their families were evacuated to Thailand by their American advisers when the Communists won control. Vang Pao lives on a ranch in Montana and other Hmong, according to the voluntary agencies that help them resettle, have adjusted well to living in various parts of the United States.

Even of the elite 2,200, however, quite a few remain in refugee camps.

The U.S. refugee program aims to give priority to people with immediate family members in the United States and those who most directly aided U.S. was efforts in Indochina.

Many of the senior Hmong officers, however, have more than one wife and polygamy disqualifies applicants under U.S. immigration law.

One of those who did qualify and has just left for the United States is Xia Ge Xiong. A former deputy chief of an area of 30 villages and 2,000 people, Xiong left Bangkok for St. Paul after first arriving in Thailand in October 1975.

He took with him his nine children. The youngest, born April 14, 1978, in the refugee camp here is named Carter Xiong.