The bright-eyed little girl in T-shirt, long pants and sneakers scurried happily about the courtroom at Fort Bonifacio, seemingly oblivious to the stern talk of the soldiers and lawyers.

To Kris Aquino, 6, it was all very natural. Her father, former Sen. Benigno "Ninoy" Aquino is the Philippines' most celebrated political prisoner and she has been in and out of courtrooms and prisons all her life. He has been in prison since she was a year old.

Now the strange murder, subversion and arms possession case against Aquino, 45, has taken another turn, and the five-year-old cause celebre may finally be approaching a climax.

After resolutely refusing to acknowledge the jurisdiction of a military tribunal during months of trial proceeding, Aquino was suddenly sentenced on Nov. 25 to die by firing squad. There was an international uproar.

Philippine President Ferdinand Marcos, who had Aquino, has leading political opponent, arrested the day he declared martial law in September 1972, quickly reopened the case. Then the Supreme Court ordered all parties to wait while it decided if due process had been violated.

Little of this is liable to please Marcos, who has been attempting the difficult task of both putting Aquino out of sight and silencing his outside supporters. The case has become a hindrance in Marcos' dealings with the United States. The State Department expressed official concern about the Aquino sentence, and Congress must eventually approve a new military bases agreement that Marcos would like to conclude.

As a measure of his growing sensitivity about the issue, Marcos has tightened his formerly relaxed stance toward journalists who want to interview Aquino. Earlier this year he denied a New York Times request to see the senator on the grounds to see the senator on the grounds that it would just build up Aquino's image. When I asked to interview Aquino this month, Marcos said he could no longer grant such permission because the solicitor general told him he had no jurisdiction. A request to military authorities for permission to see Aquino has yet to be granted.

Marcos has offered Aquino exile, probably to the United States, if he will admit his guilt, something Aquino will not do. The day may come when Marcos offers Aquino exile with no strings attached, allowing him to join the other vocal Philippine dissidents in the United States but removing him as a lighting rod for international sympathy.

To do that, Marcos needs Aquino's cooperation, which is not entirely assured. The former war hero, provincial governor and youngest senator ever elected in the country is the key symbol of resistance to Marcos' martial law rule. He has done more by simply remaining in prison than any of his fellow dissidents have done in speaking and publishing articles against Marcos. Aquino admitted to one inteviewer that he thought his job now was being in jail. His grandfather was imprisoned by U.S. Forces for helping lead the Phillippine revolt at the turn of the century, and his father was jailed after World War I for participating in the collaborationist government under the Japanese.

Some of Aquino's attorneys argue that he should stay in jail at all costs, wearing down Marcos' image as a gentle dictator and waiting for the day when he can emerge triumphant like the opposition leaders of India who won power after being imprisoned by Indira Gandhi. Other Aquino attorneys, like former Sen. Jovita Salonga, say he shoudl accept exile.

It is here that Aquino's friendly, fiery wife, Cory, 44, and their five children, especially young Kris become important.

"If my husband would not have to sacrifice his principles, then I would really do my best to convince my husband to go." Mrs. Aquino said. "I have my five children to think about. While they seem to be very normal children, I wonder what the effects will be later on."

Aquino has no more articulate or outspoken defender than his wife, and her ordeal has been eased somewhat by the Phillippine prison custom of conjugal visits.

She and the children - the other four are aged 16 to 22 - can visit Aquino in his cell, actually a room with adjoining bath, from 3 to 5 p.m. Wednesdays, 11 a.m. to 1 p.m. Saturdays and all day Sundays, Mrs. Aquino is allowed to stay all night on Saturdays.

Their first several conjugal visits were in a room with a television monitor - she threw a towel over it - and she knows everything the two of them say in his room at the prison can be listened to or recorded.

Mrs. Aquino is from a proud, political and still somewhat well-to-do family. In an interview she would sometimes grimace and clench her fists in remembering episodes of helplessness she has had to suffer during the last five years.

In 1974 she had persuaded the secretary of national defense to let her husband come home for one day. A big celebration was planned. The children were up at dawn, brushed and ready. Hours passed, no Ninoy. After a number of frantic calls, she learned that an army general at the prison had canceled the permission at the last minute.

"It was such a letdown. I learned my lesson. I never asked again," she said.

The Supreme Court, with a solid pro-Marcos majority, has halted all proceedings to look into Aquino's complaint that the military should not be trying him - perhaps the first good news Aquino has had in some time. In the end, however, Marcos holds the reins, and in the words of one veteran observer," he might want to get the case disposed of before the new bases treaty is submitted to the Congress."

Mrs. Aquino calls the charges against her husband outrageous, and most people here agree. There is no evewitness to the murder, committed five years before Aquino's arrest, and the one witness linking the senator to it changed his testimony several times. Aquino's conversations with Communists, the basis for the subversion charge is what any conscientious governor of Tarlac Province would be expected to do. The arms - a must for any politician before 1972 - may have been planted. But while Aquino remains in jail there is a taint that his wife aches to remove.

"Kris came home to say her teacher had asked some classmates what their daddies did," Mrs. Aquino said.

"I'm so glad my teacher didn't call me . . . I didn't want to say where my father was," Kris said.

"There is nothing wrong about where your father is," her mother said.

"I know that Mommy, but my classmates wouldn't understand," Kris answered.

Mrs. Aquino frowned and looked at her interviewer.

When you're six years old, a prison is a prison and only bad men go to jail."