When he was convicted of murder at age 22, Ferdinand Marcos says, he figured any chance of a political career was ended. Later, as he saw postwar Filipion leaders ignore the needs of anti-Japanese guerrilla veterans like himself, he soured even more on government.

But today, after 11 years as president of the Republic of the Philippines, the short, wiry, 59-year-old ascetic has established himself as one of the world's most successful - if ruthless - politicans.

Faced with an uproar of resentment and resistance to his assumption of martial-law powers in 1972, Marcos has still managed without much difficulty to rule by fiat for four years with on end in sight. With probably fewer arrests and less fuss than strong-armed regimes in places like India and South Korea, his government has reduced to a near shambles efforts by the church, students, Communists and professionals to organize uneffective opposition.

He has stablilized the economy, built up the army and, in the past six weeks, won a truce in a civil war waged by Moslems in the south that is perhaps the last serious threat to his rule.

"He has the potential for going on here much the way Park has gone on in Korea, or even much the way Franco went on in Spain," said a critic who both admires Marcos' political skills and decreies the jailings of hundreds under martial law.

It seems just another logical step in the charmed life of Ferdinand Marcos, fueling persistant that he has a good luck talisman implanted in his back. Son of a schoolteacher and a lawyer-politican from prominent northern Luzon families, Marcos was by his twenties a national folk hero, a heady mix of Angela Davis and Audie Murphy. The national smallbore rifle champion and the top scorer in the national bar exam, Marcos was convicted of murdering a political opponent of his father. He won an acquittal by personally arguing his case before the Philippine Supreme Court.

He fought along with the U.S. Army, was captured, tortured and then escaped to fight again as a guerrilla when Japan invaded the islands in World War II. During four years of war he collected several wounds and tropical diseases, 23 medals, including the U.S. Distinguished Service Cross, and what one diplomat here calls an unusual "guerrilla awareness" useful in politics.

"Whenever any little twig snaps anywhere," says the Marcos-watcher, "he moves to handle it."

Both the murder trial and the war left marks. For a while, Marcos says, he stayed out of politics because of disgust at what he had felt was the use of the courts to destroy him and his father, and what he took to be the recapture of the new Philippine Republic by the smae plutocrats who controlled the prewar commonwealth.

"We had hopes that the old dishonest and inefficient leaders would be replaced by a young new breed. Well, this was not the case," Marcos said recently in an interview. "An the Communist took advantage of this situation, so much so that they won to their side some of my comrades."

The war had killed his father and several other leaders of the energetic Ilocanos of northern Luzon, and Marcos was elected to Congress from the area. As a congressman, and now as president, his experiences in the trial and the war appear to have given him an unshakable confidence in his ability to overcome difficulties and a strong affection for the military in his choice of language and friends. Great power seems even to have latered his view of the murder trial thqt nearly ruined his life. In 1939, four years after the murder, the government produced a witness who said he had accompanied Marcos to the scene of the crime but whom Murcos said he had never seen before in his life. Today Marcos, himself now accused of bringing false murder charges against his political enemies, says of that trial: "I can understand it now from the viewpoint of an administrator. An assemblyman was killed mercilessly in cold blood and some kind of an action had to be taken by the state to punish a guilty party; otherwise there would be a risk of instability in the political situation."

In 1972 Marcos, saying he had evidence of several atttempts to overthrow the government, swept away much of the quarrelsome Philippine democracy with a declaration of the martial law. He was firmly supported by the men he calls "my very close friends" in the army.

By jailing or deporting those working most actively for a return to elections, threatening the Catholic Church with more taxes and a civil divorce decree, killing or capturing leading Communist insurgents and buying off Moslem rebels. Marcos has left his opposition just powerful enough to provide him with an excuse for continuing martial law.

"Everybody is split here, of course," said James Reuter, a Jesuit priest whose own mildly critical weekly newsletter was closed down by the army in December.

One secret of Marco's success appears to be what a friend calls his inability "to pull the trigger" on those who nip at his heels. The threat is there, but not often carried out. Reuter, an American, has been assured several times he is close to being deported, but he remains in the country.

Marcos appears to be personally convinced that he has ruled the 40 million Filipinos benevolently and justly, and seems unwilling to take responsibility for the excesses committed by policemen and soldiers who feeel themselves granted great license by the martial-law decree. The conflict makes Marcos seem at times almost schizophrenic. He opened doors all over the country in late 1975 for amnesty International investigators interviewing prisoners on torture charges. But he became personally enraged when a U.S. Congressional committee released a State Department report recounting some fo the Amnesty findings of torture, even though the atrocities were blamed on overzealous arresting officers whom Marcos could not be expected to supervise directly.

Marcos neither smokes nor drinks. He watches his diet, sticking to favorite dishes of his native north. "Even at banquets," says a friend, "a waiter will bring in a special bowl for him with some godawful-looking stew." He is at work at dawn and finishes the day with a round of golf, a few laps of the swimming pool and a game of pelota, a variant of racquet ball, played with some of the men Marcos has helped make very rich.

Marcos' friends and enemies agree that he and his energetic wife, Metro Manila Governor Imelda R. Marcos, have used their influence to capture several lucrative businesses for themselves and their allies. Some people, convinced of Marcos' personal frugality, argue that he is collecting the riches as a guarantee of this political power, rather than because of personal greed.

Marcos' friends, while acknowledging that official corruption still exists, insist that the situation is much improved. "So people are getting ripped off, okay," said one supporter of the president. "But at least we are getting the harbors and the roads and something's getting built. Before nothing was happening."

Western bankers and businessmen agree that Marcos has been good for the economy. The crime rate is down, tourism is up and Marcos and his wife even seem to be having success at unloading surplus sugar they have been stuck with for more than a year.

Perhaps Marcos' most difficult problem is his old friend, the United States, with its worries about human rights and its hold over vast amounts of Philippine land, trade and sympathy.He is fencing with Washington, falling back now and then to take care of more pressing matters at home.