The helicopter that carried Philippine former president Ferdinand Marcos toward exile last month hardly had taken off before opposition leaders in South Korea, 1,500 miles away, began warning their president, Chun Doo Hwan, that the same might be in store for him soon.

Talk of a Korean replay has gained some credence due to several obvious similarities. Both countries are on the Pacific Ocean's western rim, both are anticommunist, closely allied with the United States and host to its troops, and in both, authoritarian governments faced vibrant opposition movements backed by Christian churches.

But a closer look suggests that these similarities are overshadowed by the contrasts. Chun's opponents' talk of "another Philippines" seems largely rhetorical fancy. If they ever remove him, it will be for different reasons and by different means.

Marcos' 20-year reign distorted a political system that had strong democratic foundations. Korea has never managed a peaceful transition of power, and its military has argued that freedom invites attack from Communist North Korea.

Both Marcos and Chun have been called dictators by their critics, but they governed with radically opposing styles. Marcos in his final years tolerated virtually any kind of dissent that did not threaten directly his right to rule and get richer. Chun sees red at any sign of protest outside the forums he has approved. Demonstrations are broken up promptly with clubs. Books are seized and newspapers tightly controlled.

People who did pose a serious threat to Marcos' rule -- opposition leader Benigno Aquino, for instance -- ran the risk of being gunned down. On election days, Marcos would stoop to the most brazen type of cheating.

Political killings are all but unknown in South Korea. People who Chun feels threaten the order -- opposition figure Kim Dae Jung, for example -- are arrested and tried. If they are freed, they often remain under close police surveillance.

Chun wrote the rules of elections in his country, and he appears to play by them. After voting last year for a new National Assembly, the opposition submitted allegations of cheating. But there was no evidence of wholesale fraud.

In both countries, the big issue became the president himself, but for different reasons. While Marcos offered freedom to speak out, he also gave Filipinos freedom to be poor. In the eyes of many, his amassing of secret wealth was a prime factor in the country's economic malaise.

Chun allows comparatively little freedom of expression, but South Koreans generally have become more prosperous under him. Money lent to South Korea goes toward new jobs and factories, not into the president's pocket. Chun's critics condemn the high foreign debt and disparities of income distribution in South Korea. But in general, the economy is absent from their rhetoric, as it is a government selling point.

South Korea's opposition is united under the New Korea Democratic Party and enjoys strong public support, especially in the cities. It has the backing of many church leaders. But that does not bring the clout it did in the Philippines for Corazon Aquino. About 85 percent of Filipinos are Christians; in South Korea, the figure is 25 percent.

In Seoul Friday, leaders of South Korea's 7 million Protestants announced "full support" of the opposition's campaign for direct elections, United Press International reported. Cardinal Stephen Kim Sou Hwan, who leads more than 1 million Roman Catholics, announced his support last Sunday.

Historians will be a long time analyzing the role that Washington's withdrawal of support from Marcos played in his decision to leave. In essence, the Reagan administration was concerned that corruption and incompetence eventually would lead to victory by Communist insurgents. Such a victory would mean loss of the United States' largest overseas military bases.

There is no insurgency in South Korea, however. Whatever its people may think of Chun, few look on North Korea's system as any improvement. Should communism ever come, it would be through conventional invasion. This threat the South Korean government uses as a trump card in domestic politics, arguing that any disorder might lead to "misunderstanding" in the North and attack. Although some of this talk can be dismissed as an excuse to perpetuate Chun's power, memories of the 1950-53 Korean War make it a genuine concern.

Withdrawing from Korea would be a grave blow for the United States in Asia, but it would not bring the strategic paralysis that loss of the Philippine bases would.

Like Filipinos, South Koreans tend to like Americans, recalling U.S. aid during wartime. Few Koreans know it, but the U.S. Embassy prods Chun for more flexibility in dealing with the opposition. State Department officials worry that Chun's hard-line approach is courting disaster, but there is no sign that in Washington's view his policies are making an attack by North Korea more likely.

Chun also retains the backing of another crucial group that deserted Marcos in the end, the armed forces. That is due both to Chun's performance in maintaining order and growth, things the Army values highly, and to his promotion and retirement of rivals in the ranks.

Although close geographically, South Korea and the Philippines have vastly different cultural traditions and national personalities.

Filipinos are a fun-loving people, with dashes of the Spanish and American world views. Aquino rallies could be mistaken easily for fiestas, with their balloons, streamers, firecrackers and foods.

In the end, Marcos lost out to what Filipinos now know as "people's power." Each time he tried to send soldiers to crush a military rebellion, thousands of festive civilians would surround his troops and shame them into going back.

Chun's opponents tried "people's power" in 1980 in an uprising in Kwangju to protest his consolidation of control over the country. The troops opened fire. When the smoke cleared, close to 200 persons were dead by official count, and Chun was still on top.

Korean culture has a strong Confucian heritage, which stresses authority and learning. People approach life with an underlying seriousness. Their politics is often compared to heavyweight boxing, with each side slugging away in search of a knockout.

By most accounts, South Korea is going to have a lively spring politically, as the opposition vigorously presses its campaign to unseat Chun. There will be little use, however, in looking for parallels with the Philippines. The Koreans have their own way of doing things.