THERE IS A NEW bumper sticker in California that reads: "El Salvador Is Spanish for Vietnam."

The Reagan administration has made this comparison inevitable by urging an extensive pacification program for rural El Salvador at the same time it is asking for increased military aid.

As a social scientist who once studied the pacification program in Vietnam, I find myself being asked whether such a program can work in El Salvador. That is, will new roads, schools and clinics along with expanded local government in control of a local militia make a difference to the campesinos? (In Vietnam, after all, the pacification program did enable the Saigon government to establish control over most of the country.)

To believe that local government and infrastructure will win campesino support while lawless violence rages is to ignore a major lesson from Vietnam. The question Congress should be asking is whether it makes any sense at all to bother about such programs in El Salvador when the most elemental form of pacification -- physical security -- is denied to rural people by its own government.

The lesson from the pacification program in Vietnam is that the control of violence is more important in a long war than programs to improve rural welfare. The successes of the pacification program in Vietnam resulted not from capital projects and local government but from bringing a measure of physical security to the everyday lives of the villages.

What villagers appreciated was the ability to go to their fields without being abducted and to retire at night confident that they would not be killed in their sleep.

It took a long time for the American and South Vietnamese military to learn that how they fought the war affected the response of the peasants to the Saigon government. Too often when guerrilla forces were reported in a village, the military bombed the village. When villagers reported that a neighbor had talked with guerrillas, the neighbor was arrested or killed. The villagers quickly learned that it was very costly to cooperate with the armed forces no matter how strongly they opposed the guerrillas.

The suppression of violence will be harder in El Salvador. In Vietnam, the violence the peasants feared most was misdirected American firepower. The pacification program put American advisers into positions from which they could protect peasants from our lethal weaponry. In El Salvador,there will be no American advisers with such authority and there are two sources of violence to be controlled: the regular military and the quasiofficial death squads.

In El Salvador, campesinos fear indiscriminate killing by the regular military and by death squads carrying out secret executions at the behest of, or with the acquiescence of, military officers or landowners. In addition to controlling the regular military, any pacification program must bring these death squads to heel. Any program that tries to coopt these groups or make them its agents without controlling their violence will fail. More than that it will increase the likelihood of a bloodbath by giving them a new license to practise terror.

In Vietnam, there were thousands of American civilian and military advisers to protect the pacification program and those who administered it. In the absence of such protection in El Salvador, could rural officials stand up to the regular military or the death squads? What then would their lives be worth?

The temptation for the Reagan admininstration is to not confront the problem directly but to defer it to a later time. This is what all past administrations did in Vietnam.

The electoral cycle leads our presidents -- in Richard Betts' phrase -- to nibble the bullet rather than bite it. With a presidential or congressional election always imminent, every president chose to buy time in Vietnam rather than to risk the short-term costs of reform. Reform risks destabilizing a government or provoking opposition on the right but it is necessary if there are to be any long-term gains.

Without reform, pacification merely defers collapse and raises the stakes. The next president will inherit a larger war to which more of the nation's prestige has been committed.

If the lessons of Vietnam are to be applied to El Salvador, the president and Congress must ensure that any commitments that raise the stakes in El Salvador will increase the chance of ultimate success.

The price of any further aid to the government of El Salvador must be its readiness to deal ruthlessly with indiscriminate killing. In the long run, it is easier for a government to maintain its authority if it can claim credit for protecting the lives of its citizens than if it provides roads and schools while leaving citizens' lives at risk.

In El Salvador as in Vietnam, real pacification must follow the priorities people everywhere acknowledge, be they peasants or philosophers. The fundamental human right is still the right to life.