MANILA -- When the heads of government of the Association of Southeast Asian Nations first met in Bali in 1976, there was a strong sense of urgency. Communist regimes had achieved surprisingly swift victories in Vietnam, Cambodia and Laos, while the United States, humiliated by its costly Indochina foray, retreated from the region.

Today, the expanded six-member association, known as ASEAN, began only its third such summit in its 20-year history, meeting for two days under heavy security precautions. Up to 10,000 troops set up checkpoints yesterday and today on bridges, major intersections and key approaches to the city. Six Indonesian and four Malaysian ships joined Philippine Navy vessels in the harbor near the site of the summit.

This time, however, the member-states of Thailand, Indonesia, Singapore, Malaysia, the Philippines and Brunei seem to be groping for a new focus.

The goals of economic cooperation enunciated at the group's founding meeting in Bangkok -- and reiterated in Bali -- have collided with a worldwide recession, reduced prices for ASEAN's commodities, and the reality that the member-states' economies are essentially competing with each other.

On the political side, the "threat" of a revolutionary, expansionist Vietnam, which provided a potent rallying cry following Vietnam's 1978 invasion and occupation of Cambodia, appears to have dissipated somewhat.

Under a new reform-minded leadership, Vietnam has turned its attention to improving its battered economy. Meanwhile, some of the ASEAN countries who led the call to "isolate" Vietnam economically and diplomatically are now among Hanoi's leading noncommunist trading partners, trying, as one Indonesian journalist put it, "to prepare for the post-Cambodia era," presumably following the withdrawal of Vietnamese troops.

"What ASEAN does not have, and what the European Community does have, is NATO," said Prof. Juwono Sudarsono, a political scientist at the University of Indonesia. "The Europeans have a real sense of imminent danger -- that's what made the economic positions more forthcoming. Here, there is no common denominator of sufficient urgency to have economic cooperation put into the context of regional cooperation."

"They have to make some sort of agreement for more regional cooperation, otherwise it will look very, very bad," said Thailand's Prof. Sukhumbhand Paribatra, director of policy studies for the Institute of Security and International Studies at Chulalongkorn University.

Even the one common notion agreed to in the founding Bangkok meeting, that ASEAN should strive to become a region of peace and neutrality, has proven elusive, partly because of a recent debate here over the desirability of the United States' two large military bases in the Philippines.

When Foreign Secretary Raul Manglapus suggested in October that ASEAN should reach a "consensus" on whether the American bases contributed to regional security, he was looking for a way to placate domestic public opinion.

But his suggestion, which he has since tried to play down, exposed deep divisions within ASEAN over perceptions of the region's greatest threat.

Although the summit is likely to conclude with an economic agreement, questions and pressing issues far more important to the region's future growth, development and security will not be on the agenda, at least in public, because of concerns of maintaining a united front and avoiding matters that are deemed internal or bilateral.

ASEAN leaders will not be discussing the future of American military bases in the Philippines, since that has been called a bilateral matter between the United States and the Philippines, even though the possibility that the bases may have to be withdrawn after 1992 would force ASEAN to rethink its security arrangement.

Nor will they be discussing publicly the growing communist insurgency in the Philippines, even though some member-countries have expressed grave concern in private over the course of the war here.

A third issue has to do with democratization and political succession.

The question of future leadership is important because it portends much for the one clear success of ASEAN over the last 20 years -- the virtual elimination of hostilities between member countries.

Singapore's Lee Kuan Yew has served as head of his People's Action Party and prime minister for a quarter of a century, and has indicated he might step down next year. Indonesia's President Suharto has served for 20 years since taking power in a military coup and has said he will ask for a fifth -- and probably final -- five-year term next April. Thai Prime Minister Prem Tinsulanonda had earlier given hints that he would step down next year. Philippine President Corazon Aquino, who is widely viewed as the only leader in her country capable of providing political stability, is barred from running again when her term expires in 1992.

The succession question in the region must also be seen against the backdrop of the Philippines' middle-class-led 1986 revolution that overthrew the 21-year dictatorship of Ferdinand Marcos. Many political analysts, journalists, academics and foreign diplomats in various countries around the region have said that the Philippine revolution appears to have unleashed or inspired centrist, democratic forces elsewhere in Asia, such as in South Korea, where student-led protests joined by the urban middle-class forced President Chun Doo Hwan to accept a package of democratic reforms.

For the ASEAN countries, analysts and diplomats say the most unsettling issue for the future is fostering more democratization, which has not kept pace with the region's impressive economic performance. Indonesia and Thailand are essentially still run by the military. Dominant political parties in Malaysia and Singapore have resorted to measures often described by outsiders as harsh to quash most forms of internal dissent, including using sweeping "internal security acts" held over from the British to round up political critics. The press has few freedoms in most of the countries, except the Philippines.

In all of the countries except the Philippines, "there is an absence of an accepted mechanism for change, so there is always a potential for instability," Thai professor Sukhumbhand said. "The Philippine revolution showed everybody. The practices of Marcos, while excessive, were not very different from the practices elsewhere. Cronyism, semiauthoritarian government -- these things have been a feature of Southeast Asia for a long time."