View from Bangkok: defense and economy are shared concerns

''Build and defend the country.'' The slogan is Vietnamese. But it could just as easily be Singaporean, Thai, or Malaysian.

For in this sharply polarized region, both the five members of the Association of Southeast Asian Nations (ASEAN), on the one hand, and the three communist Indochinese states (Vietnam, Kampuchea, and Laos), on the other, all share a preoccupation with the economy and regional security.

Kampuchea continues to be the immediate security problem. Some ASEAN countries see advantages as well as problems in the present confrontation with Vietnam. Singapore's prime minister, Lee Kuan Yew, for example, recently told an interviewer from Japan's Mainichi Shimbun newspaper that ''as long as the geopolitical situation remains unchanged, with the Vietnamese in occupation of Kampuchea and locked in an unwinnable conflict against China, the other countries of Southeast Asia will be left free from subversion.''

But ASEAN will soon have to make some important decisions about its material assistance for the coalition. Singapore and perhaps other ASEAN members recently gave the forces of the noncommunist faction led by Son Sann substantial military supplies. But those forces recently suffered considerable losses during the Vietnamese attack on one of their bases in the refugee camp of Nong Chan near the Thai border.

How much weaponry is ASEAN willing to replace? And how often? And if, as some observers now expect, the Vietnamese try soon to destroy the bulk of the Son Sann forces, is ASEAN ready to reequip them from scratch?

Vietnam, too, is standing firm. In Hanoi's view, Kampuchea is a matter of survival. Vietnam can be safe from a Chinese threat only if a firm ally in Phnom Penh is defending Vietnam's western flank.

The tightening of relations among the three Indochinese countries that has been discernible in recent months underlines Hanoi's belief that no change is possible in the Kampuchean status quo. A summit meeting of Indochina leaders was held late in February.

One source of relief for Hanoi is the improvement in the Vietnamese economy last year. The latest harvest was the best ever, and Vietnamese planners are hoping to achieve food self-sufficiency next year. The improvements are mostly due to policies that stress results and incentives over ideological considerations.

But a cloud is forming on the horizon: the future of Soviet aid. As a precondition for better relations with Moscow, China has demanded that the Soviets cease all aid to Vietnam until it withdraws its troops from Kampuchea. Moscow has reportedly rejected the idea, but the demand, coupled with persistent reports of Soviet unhappiness at Vietnam's inefficient use of Russian largesse, underscores Hanoi's vulnerability to outside pressure. The late-February announcement of some troop withdrawals appears, as a direct result of Soviet lobbying, to go further toward meeting the Chinese demand than such announcements in the past.

The Soviets, however, benefit considerably from their relationship with Vietnam. They have access to two important bases for their military aircraft and shipping, and with this comes ASEAN's unwilling recognition that Moscow has to be included in any consideration of regional security.

Under Yuri Andropov, the Soviets have taken a more active diplomatic role in the region. Soviet Deputy Foreign Minister Mikhail Kapitsa's recent visit to Bangkok assured the Thais that Vietnam did not intend to violate Thai territory in pursuit of anti-Vietnamese guerrillas. The Thais appear to have toned down protests over Vietnamese military actions.

The security question has been complicated by the possibility of Sino-Soviet rapprochement. China may have been playing a fairly positive role in the region recently, but what will happen if it normalizes relations with Moscow?

ASEAN hopes Moscow's desire to satisfy the Chinese toward normalizing relations will make it pressure Vietnam to negotiate a solution to the occupation of Kampuchea.

In general, the growth of Soviet presence in Southeast Asia has coincided with the decline of US presence here, and ASEAN is still looking for ways to maintain a regional balance of power.

To some degree ASEAN itself is trying to fill the gap. Its member nations are acquiring more sophisticated weaponry. Thailand has suggested standardizing ASEAN military equipment and creating a pool of military supplies which each country can tap in time of need.

Singapore has made some more controversial proposals, including joint ASEAN military exercises. The idea has been greeted coolly by Singapore's partners, who do not want to turn the association into a regional military alliance. Singaporeans also tend to feel that the Chinese have played a positive role in regional security recently, whereas other ASEAN countries continue to fear the return of Peking-backed insurgency movements. And unlike most ASEAN countries, Singapore supports the US position that Japan play a more active role in Asian defense.

The most pressing problem currently facing ASEAN, though, is one for which it has no solution: the impact of the world recession, which has cut deeply into the economic growth rates of ASEAN members.

Singapore, which has averaged 10 percent annual growth in the last 15 years, may be down to 2 or 3 percent this year. With an average per capita income of $4 ,000 a year, Singapore can perhaps take the strain more than most. Even so, Mr. Lee has warned that his country ''can stand recession in America and Europe for two more years, but not more.''

Neighboring Malaysia is rich in resources. In 1982 it produced one-third of the world's tin and most of the world's rubber and palm oil. But prices of all three commodities dropped disastrously. Rubber prices, for example, plunged 21 percent, due mainly to auto industry cutbacks in the West.

An effort to create a tin producers' association - a tin OPEC - has not yet come to fruition.

Malaysia's GNP growth rate dropped from its five-year average of 8.5 percent to 2.8 percent last year, and now the government is cutting back on spending, particularly in its cherished development projects.

Although most of the ASEAN economies are strong enough to weather the recession, question marks hang over Indonesia and the Philippines.

Indonesia is essentially a one-commodity economy - 70 percent of its export revenues come from oil and gas. The drop in world oil prices has worsened its financial plight. In 10 to 15 years its oil will probably be gone, and belated efforts at diversification have been checked by the recession.

The future of the Philippines seems even more problematic. The economy is in serious straits. Last year, for example, it announced a balance-of-payments deficit of $1 billion, and the government has had to cut its spending programs. Questions about the health of President Marcos have still not been satisfactorily answered.

Meanwhile local and foreign observers alike are worried by the hazy plans made for any succession to Mr. Marcos's authoritarian rule. In the countryside the communist guerrillas of the New People's Army are growing in strength and influence, and are talking of moving into a new, more intense level of guerrilla war.