A congressional fact-finding mission arrived here today for talks with Vietnamese leaders about controlling the flow of Indochinese refugees that has threatened to destabilize neighboring Southeast Asian countries.

The nine-man House delegation landed at Noi Bai military air base, two hours by car from Hanoi, after a flap during which the Communist leaders canceled the visit, then reversed themselves after U.S. diplomatic approaches.

Rep. Robert F. Drinan (D-Mass.), who stirred Hanoi's anger by calling Vietnam's traffic in refugees the worst human rights riolation of the century, said before landing that he was not recanting a word.

"If anything, I'll be coming on stronger," he said. The priest-politician was wearing a colorful sports shirt instead of his usual clerical black suit with Roman collar.

The congressmen, who will leave Thursday for Washington after less than 24 hours in the Communist capital, had no inkling of what sort of reception to expect from the Hanoi leadership.

Delegation leader Benjamin S. Rosenthal (D-N.Y.), said the group wanted to find out what the Hanoi government will do to carry out commitments made at the recent Geneva conference on refugees on providing for an orderly flow of people who wish to leave the country.

U.S. refugee officials estimate that from a third to half of the refugees leaving Vietnam perish at sea.

One U.S. proposal is that American consular officials be allowed to set up temporary offices in Ho Chi Minh City, formerly Saigon, to expedite the departure of Vietnamese with relatives already in the United States. The congressmen were carrying a list of 5,000 such cases.

Hanoi has said it is ready to export 600,000 people at a rate of 10,000 monthly if and when the United States is ready to receive them.

The United States has countered that there are more than 380,000 Indochinese refugees now scattered in camps across Southeast Asia who must be resettled.

The congressmen have visited nine refugee camps in four countries in five days. They found spirits high among 33,000 refugees on Bidong Island, a Malaysian refugee camp, during a visit there this morning before their departure for Hanoi.

It was apparent that the Geneva conference, at which several Western nations agreed to increase their refugee intake, had made all the difference.

"Now there is hope for us that we will soon be leaving here," said Tran Minh Khiem, 29, a graduate of the University of California at Berkeley.

Khiem reached the one-square-mile Bidong Island May 12 after a harrowing seven-day voyage. He said that his boat, which carried 557 persons, was attacked seven times by Thai pirates.

"Several of our women were raped," he said. "And one of them committed suicide by jumping into the sea."

"Now that the refugee population is being reduced by resettlement," said the Rev. Le Ngoc Trieu, 47, camp leader, "we have a little more room to live and breathe in." CAPTION: Picture, Congressional delegation leader Benjamin Rosenthal talks in Hanoi with Foreign Ministry official Vu Hoang.