The impact on the Washington area Buddhist community of the massive influx of Vietnamese since the fall of Saigon in May 1975 was demonstrated at the recent celebration of Buddha's 2,522 birthday.

The community-wide celebration of the major Buddhist festival, called Vesak for "full moon," was held in the moonlit garden of the Vietnamese temple at 5333 16 th St. NW.

The temple, in existence for only two years, already is inadequate to house what has quickly grown into Washington's largest Buddhist congregation. It is estimated that "thousands" of Vietnamese have settled in the area, and more are coming here each week.

Before 1975, the largest concentration of Buddhists was a few doors away at the Buddhist Vihara, the Sri Lankan temple. Within that group, however, the majority of the 600 members are American.

Last Saturday night, the 1.300 worshipers, who also filled the adjacent backyard of a missionary order of Catholics, the Sisters of Africa, formed an international meeting of Buddhists - Japanese, Cambodian, American, Korean and Thai. But the overwhelming majority were Vietnamese.

Priests from the area's smaller ethnic temples faced the glittering orange-and-red altar, offering prayers before a Buddha whose feet rested above as Indochinese-centered world globe.

The highlight of the evening came during the main address by the Venereble Thich Giac Duc, now head of the Vietnamese Buddhist Congregational Church of America. He introduced the Venerable Oung Mean Candavanna, president of the Cambodian Buddhist Society.

Alternately, the two priests read a point statement deploring the border disputes between their homelands, asking that Buddhists should not "raise arms against each other."

The tragic border wars broke out early this year between the Vietnamese nation of 50 million and the 7 million population of Cambodia, the latest flareup of ancient animosity between the two ethnic groups that was put aside during the war in which the U.S. participated.

But the strong Vietnamese presence dictated the theme of Saturday's ceremony, an emotional account of the plight of the Vietnamese people, both in the homeland and in the Diaspora.

"At no time have we suffered more than now." said Tang Xuan An, "with our people in reeducation camps, suffering the greater loss of our freedoms. Many of us have been forced to flee our homeland. . . . We are looking to Lord Buddha for guidance."

Figures on Vietnamese complied last year indicate that 10 percent are Roman Catholics. The rest identify themselves as Buddhist, although only 10-20 percent are active in the faith. Some of these belong to offshoots of Buddhism such as Dai, a mixture of many faiths.

Their stateside spiritual leader, Giac Duc, is former secretary general of the council of representatives of the Buddhist sects of Vietnam based, before the war's end, in Saigon. In 1972, he ordered Buddhist monks to disregard then-president Nguyen Van Thieu's instructions to join the army-Devout Buddhists are forbidden to kill.

Saturday, Giac Duc's anti-Communist sentiments set a tone for the migrant celebrants which was reflected by many, who offered grateful prayers for the opportunity to settle in a "free land" following the war.

Giac Duc offered a special prayer for the "boat cases," Vietnamese refugees constantly being turned away from foreign ports as they seek a place to migrate. Tuesday. Reuter reported that 85 people landed on Philippine shores where they will be formally charged with illegal entry and sent to crowded camps in Manila until another country can be persuaded to take them.

Sunday, an American container ship rescued 58 Vietnamese from a leaking boat in the South China Sea.Last week a group of 35 in similar circumctances were picked up by another American vessel.

The festival itself is a celebration of the life of Gautama, an Indian who retreated from the world to contemplate and returned with a spiritual plan to relieve suffering. The plan, was accepted so enthusiastically that he was called Gautama "Buddha" or "The Enlightened One."

The tradition of recounting Buddha's life is of vital importance to Buddhists because his is the model life that they must emulate to achieve "nirvana," the perfect state in which he conquered the "defilements." The "defilements" of greed, hatred and ignorance are thought to imprison all beings on the wheel of life as they are constantly being reincarnated, constantly suffering.

When Buddha died, he went to a happy state of rest, breaking the yoke of cyclical corporeal (bodily) existence.

"The defilements pollute the mind causing turmoil inside and out," the Venerable Bodhi, an American Buddhist in a robe of rusty orange told the crowd.He said the defilements infect society as well as individuals.

Later, a group of children presented flower gifts of azaleas to the halo-crowned cherubic Buddha smiling down from over the altar.

Giac Duc completed the liturgy with a chanting of prayers punctuated by the majestic sound of a bowl gong.

Afterward, a small rock band played music and children and young people danced in the still air under the bright, full moon. A woman, too tired for a party following the three-hour service, stopped to listen to one song she described as "sentimental" because "it is about our homeland."

The festivities ended after a procession of children marched down the street carrying lighted paper lanterns to the Buddhist Vihara, where they ceremonially walked three times around the building.