Salvador colonel who mutinied is back in war.

Lt. Col. Sigifredo Ochoa Perez stands on the back of his army jeep before a crowd gathered on the grassy town square. The colonel, resplendent in pressed combat fatigues and aviator sunglasses, carries a shiny black Berrita machine gun over his shoulder.

He waits as his troops direct people to gather around him. And then he tells residents that he intends to reestablish the Army's presence here in Chalatenango, a rugged mountainous province that is largely under guerrilla control.

The public speech is one of Colonel Ochoa's first since returning to El Salvador after 11/2 years in diplomatic exile. It marks a return to grace of one of this country's most controversial military commanders.

It was Ochoa whose rebellion against former Defense Minister Jose Guillermo Garcia led to the general's resignation from the top military post in 1983. For that act Ochoa was banished to a diplomatic post in the United States.

But he had established a reputation as a smart strategist in counterinsurgency, won the admiration of many United States military advisers, and managed to wipe out many of the guerrilla operations in Cabanas Province. So , earlier this month, he was called back to serve in one of El Salvador's most important and most difficult command posts.

''Many people in the party didn't want Ochoa to come back,'' says a high-level political adviser to Christian Democratic President Jose Napoleon Duarte, ''but the US insisted.''

Today, as he tells peasant farmers in La Reina about the importance of carrying identity cards, troops are busy putting posters around the town that say the Army defends freedom of worship and human rights. The soldiers also have cans of black paint and brushes to blot out revolutionary slogans on walls.

''Should we run and hide when we see the Army troops coming?'' a farmer asks Ochoa.

''No,'' Ochoa answers, ''we only shoot those who are armed. We respect private property.''

The human rights bureau attached to the office of the Roman Catholic archbishop in San Salvador, however, has already charged that troops under Ochoa's command in Chalatenango massacred some 40 unarmed civilians in a recent Army sweep in the north of the province.

This is the second alleged Army massacre of civilians in the last two months. In the preceding 12 months there were only three alleged massacres, according to the Catholic human rights office.

''So they say we have massacred civilians,'' Colonel Ochoa says as he stands on the shaded porch of the mayor's office after the La Reina town meeting. ''Where are the victims? We turned some people over to the International Red Cross; perhaps they mean them. The Marxists see our military advances and they have no military capacity, so they create this propaganda.''

Troops under Ochoa's command were accused of massacring civilians at an earlier stage of the war as well - in November 1981.

Ochoa, sipping a warm bottle of Coca-Cola, likewise discounts the possibility of a major rebel offensive in the next few months.

''This talk of a big offensive is the creation of the North American press,'' the colonel says, apparently unaware that US President Ronald Reagan predicted a big Tet-style offensive by the guerrillas several weeks ago. ''The subversives don't have the capacity to do much damage,'' Ochoa asserts.

Ochoa is widely regarded as politically, as well as militarily, shrewd. His six-day mutiny against former Defense Minister Garcia in 1983 started as a protest of his scheduled reassignment to the Salvadorean Embassy in Uruguay.

But the colonel, a close confidant and classmate of Roberto d'Aubuisson, the cashiered Army major who was defeated by Mr. Duarte in this year's presidential election, turned the protest into a move by ultra-rightist military officers to force Garcia out of office. In a compromise that many observers contend heavily favored Ochoa, Garcia agreed to resign if the rebellious colonel was sent to the US.

Ochoa was reassigned to Washington. Garcia stepped down, and since that time has spent his time shuttling between El Salvador and Miami, where, according to Salvadorean military sources, he owns extensive property.

Ochoa's return to El Salvador is not, however, his first rehabilitation. He was banished to diplomatic obscurity in 1979, a common fate for military officers who are accused of involvement in gross human rights violations, after being implicated in the murder of a sacristan in a working-class neighborhood of San Salvador. At the time of the murder, Ochoa was the acting director of the Treasury Police, a unit many US officials contend was strongly linked to death-squad activities.

Several citizens of La Reina say Ochoa's announcement that he will put the town under Army control will only ensure another rebel attack.

Rebel forces overran La Reina a year and a half ago, killing two of the national policemen stationed here and capturing the remaining 22. The steady advances of the guerrillas in the province left only three towns in the area with permanent concentrations of troops.

''The guerrillas were here yesterday afternoon,'' a town resident says. ''They said they were leaving because the Army planned to arrive in the morning.''

The colonel departs after little more than a hour in La Reina. As he leaves, an Air Force helicopter, one of 10 new Hughes 500s that arrived this month, swoops down over the town square. The troops begin to withdraw, taking with them a man accused of murdering his brother. The man had been apprehended and placed in the town jail three days earlier by rebel authorities.