A 22-year-old South Korean immigrant who joined the U.S. Army last year reportedly has surfaced as a defector in North Korea two months after he disappeared from his unit in West Germany.

North Korea's official Pyongyang Radio has announced that Pfc. Chung Ryeu Sup, 22, had defected to North Korea because he "could no longer endure the disgraceful life of national insult and maltreatment he had to lead in the U.S. imperialist aggressor Army."

Also known as Roy Chung, the soldier disappeared in June while serving with an U.S. Army unit near Bayreuth, West Germany about 30 miles from the Czechoslovak and East German borders. His parents, who live at Glendora, N.J., said they are convinced their son was abducted by North Korean agents.

Chung, who is not a U.S. citizen, immigrated to the United States with his family in 1973. According to his father, he joined the Army last year to get Army education benefits.

State Department and Pentagon officials said that while they had no information about Chung's whereabouts, they had little reason to doubt that he is in Pyongyang, as North Korea claims.

The Army first reported Chung absent without leave on June 5. After 30 days, he was classified as a deserter.

"We haven't gone to extraordinary lengths to investigate it yet," an Army spokesman said, pointing out that Chung had no access to classified documents and as such would not be considered a security risk even if he had defected to the Communists.

Calls to local police officials in West Germany indicate that the Army has not asked for their assistance in investigating Chung's disappearance.

The soldier's father, Soo-Oh Chung, 50, said in a telephone interview this week that he first learned that his son was missing in the Aug. 11 edition of a local Korean-language newspaper. The Army, however, says its records show that the family was notified of the soldier's status after he was declared AWOL and again when he was classified as a deserter.

Although he has no concrete evidence that his son was abducted, Chung, an auto mechanic in Glendora, N.J., said he is convinced that North Koreans forced his son to go to Pyongyang.

"The word 'defection' cannot be used," Chung said. "It upsets me. It just cannot happen; it is abduction."

Other Koreans have cited about a half dozen other cases in which North Koreans allegedly kidnaped or attempted to kidnap South Korean citizens abroad, usually in Europe, Japan or Hong Kong.

In April, a geology teacher from Seoul who was attending a course in the Netherlands was on vaction in Oslo when he disappeared. His passport and an unmailed letter home were found on a city bus. Two months later, the teacher was reported by the North Koreans to be in that country, but many South Koreans say they believe he was kidnaped.

In a celebrated case, well-known actress Choi Eun Hui disappeared in Hong Kong in 1978 after having contact with two persons believed to be North Korean agents who invited the actress to participate in a bogus film project. She has not been heard from since.

A State Department source said that while he was familiar with several such cases, it is usually impossible to prove abduction by Communist agents.

Korean-American groups have formed committees to bring the matter to the attention of Congress and persuade the State Department to pursue it more vigorously, and the active Korean-language press has published several articles about Chung's case.