Japanese Prime Minister Yasuhiro Nakasone's first state visit to Southeast Asia ended here Monday, with the Japanese reportedly satisfied that they had successfully negotiated a tightrope of delicate talks on defense, trade and foreign policy.

On the surface, the purpose of the visits to the five member countries of the Association of Southeast Asian Nations (ASEAN) and Brunei was for Nakasone to lay out a variety of commitments by his country that were aimed at increasing Japan's access to the resources and markets of the ASEAN states in exchange for technology transfer and economic aid.

Underlying the meetings, however, was what observers saw as Nakasone's need to reassure ASEAN governments--particularly Indonesia and the Philippines--that Japan has no intention of returning as a major military power in Southeast Asia.

There was little expectation that the tour would set Japanese foreign policy in a new direction, but Nakasone appeared clearly determined to establish an uncontestable and expanded role for Japan on a long-term basis with the growing economies of ASEAN. He said Monday that he viewed the ASEAN region as the area in the world "full of the greatest dynamism and potential for the future."

Having already made contacts in the United States and South Korea, Nakasone seemed equally determined to forge personal relations with the ASEAN leaders that could help Japan achieve a leadership role as ASEAN grows as a regional power.

In the light of last year's controversy over revisions of Japanese textbook histories of World War II Japanese atrocities in occupied Asian countries, sources said, it was more essential than ever that Nakasone take special care in establishing personal trust and communication with his counterparts.

Announcements earlier that Japan and the United States are starting talks on the Japanese assumption of defense over two important sealanes--one southeast to the Bonin Islands and the other southwest toward Taiwan--had alarmed some of the ASEAN leaders.

One exception to the general discomfort with an increased military profile for the Japanese was Prime Minister Lee Kuan Yew of Singapore, who, according to sources, viewed the shift of responsibility to Japan for regional defense as an opportunity for stronger U.S. defenses against growing Soviet naval presences elsewhere.

President Suharto of Indonesia reportedly made it clear to Nakasone that Indonesia could support the sealane plan only in the strictest framework of defense.

Nakasone reiterated Monday that Japan, while breaking the postwar taboo on public discussion of its military posture, has no intention of changing its constitutional commitments to only a minimum self-defense capability and a renouncement of nuclear capability.

"This is more than a matter of policy: it is deeply rooted in strong and unchanging Japanese national sentiments deriving from our sincere contrition about the past," he said.

On the trade side, Nakasone gave assurances that Japanese trade practices, seen here as broadly self-serving, will shift to a more equal exchange.

Because of domestic financial and political pressures, however, Nakasone was unable to commit Japan to specific aid programs in the ASEAN countries, and he simply said he would lend his support to such demands when presenting them to the private sector.

Before leaving Japan, Nakasone had promised a 50 percent increase in industrial imports under the General System of Preferences, starting in 1984. No new concessions were announced on the trip.

Instead a general plan for scientific and technical exchange at the ministerial level was outlined, a promise was made to aid in the renovation of aging Japanese-built industrial facilities and a five-year exchange program for youth was proposed.

Nakasone, who was twice minister for science and technology, was expected to emphasize exchange of technology on his tour. But apart from the promise of a survey by the Japanese International Cooperation Agency for the renovation of railways, his announcements were criticized for their lack of details or guarantees.

At the same time, Japan made some requests of its own. During his talks with Malaysian Prime Minister Mohammed Mahathir, Nakasone said Malaysia would have to cut its oil prices in order to increase petroleum exports to Japan.

In Jakarta he had already promised Indonesia to try to keep Japanese oil imports from there at 15 percent of Japan's total oil imports. Unlike in Malaysia, oil is Indonesia's main export earner, and the drop in the Organization of Petroleum Exporting Countries' prices has caused a full reevaluation of that member nation's economic planning.

For Thailand and Singapore, foreign policy support from Japan was of greatest importance. To both, Nakasone reiterated his support for the Cambodian coalition fighting the Vietnamese-backed Heng Samrin government and promised a freeze on major aid to Vietnam until the withdrawal of Vietnamese forces from Cambodia.

Nakasone also said he would convey the international concerns of ASEAN leaders to the Williamsburg economic summit meeting at the end of this month.