MANILA, Philippines (AP) _ President Corazon Aquino said Thursday that Ferdinand E. Marcos cannot return to the Philippines unless he repays billions of dollars her government says he stole during 20 years in power.

A popular rebel Roman Catholic priest, interviewed in an undiscosed location, said he would not comply with Mrs. Aquino's appeal for insurgents to surrender. An army official reported three deaths in a battle with the largest group of communist rebels troops have encountered since Mrs. Aquino took power when Marcos fled Feb. 26.

Marcos has said repeatedly that he wants to return home, and in recent radio interviews from Hawaii has encouraged followers who have mounted street protests against the new government.

His loyalists demonstrated in front of the U.S. Embassy for the third day Thursday, demanding his return. They claim that the United States ''kidnapped'' Marcos when the U.S. Air Force flew him to Hawaii and that the Americans installed Mrs. Aquino.

In her comments, Mrs. Aquino scotched reports that she might let the former president keep some of his money.

''I have been asked, 'Is there any way for Mr. Marcos to return to this country?' and I've said that perhaps a starting point would be for him to return all of the ill-gotten wealth,'' she said in an interview with ABC Television that was broadcast in Manila.

Her government charged this week that Marcos, his relatives and associates stole $5 billion while he ruled this archipelago of 55 million people.

Mrs. Aquino released her own financial statement Thursday. It gave her net worth as 17.7 million pesos ($880,000).

Financial statements of other members of the administration also were made public. Presidential spokesman Rene Saguisag said the purpose was to ''change the grain of political morality.''

Philippine representatives have begun formal procedures in Switzerland in an attempt to reclaim hundreds of millions of dollars Marcos and his associates are said to have deposited there.

In other matters, there had been several reports that the Rev. Conrado Balweg, who left his parish north of Manila in 1980 and joined the rebels, was considering surrender.

He has become a folk hero to many disaffected Filipinos, posing in widely published photographs carrying automatic weapons. Poetry has been written about him in rural elementary schools, and his reputation grew after Marcos offered the equivalent of $11,000 as a reward for his capture.

''Why should I surrender? I was never a criminal,'' he said in an interview with June Keithley, a children's show host on government television who met him in a wooden hut at an undisclosed location.

''Our life is linked with the interests of the masses,'' Balweg said, ''so what do we have to surrender? Do we have to surrender the interest of themasses?''

Capt. Julasiri Kastiri of the army information office said a soldier and two insurgents were killed in a battle Tuesday at South Cotobato on the large southern island of Mindanao.

He said the fight was between 200 rebels and a group of military trainees who ran across them during an orientation course in the Mindanao mountains. A corporal acting as an instructor was killed, a trainee was wounded and another was missing, he said.

One rebel was captured in the conflict, which the state-run Philippine News Agency described as the heaviest fighting with insurgents since Mrs. Aquino took office two months ago. Neither Kastiri nor the agency said how many soldiers took part in the battle.

Communist rebels fought Marcos nearly as long as he was in office. The insurgency had been growing, and the United States pressed him in recent years to reorganize the military so it could deal with the threat more effectively.

Mrs. Aquino has asked the rebels to lay down their arms, contending that they have no reason to fight now that Marcos is gone.