With just over a month left before the first national election held here in more than 15 years, Peru's military leaders, political parties and citizens are discovering that the return to democracy is not as easy as they had hoped.

Within the military government, officers are still bickering over what kind of election should be held, and what powers of the elected civilians should be.

One of Peru's leading political parties, which was in power at the time of the 1968 coup that brought the military to power, has pulled out of the election process in a huff over the same issues.

Many people outside the relatively sophisticated capital remain unconvinced that an election will be held at all, fearful of its consequences, and unclear as to its purpose.

"They are going to elect a new president," said one Peruvian, incorrectly, as he stood watching a political rally in his small village square, 50 miles south of Lima.

Like most of his neighbors, the villager observed the campaign activity, a cacophony of blaring horns, loud-speakers and frenzied party organizers carrying around banners and posters, from a distance. As he talked, he glanced nervously at a group of policemen standing on the other side of the square.

On June 4, Peru will become the first of six nonelected military governments currently in power in South Americo to hold an election. The nation's 5 million voters will select a 100-member assembly to write a new constitution - Peru's 13th since independence in 1822.

The constitution will outline a program for electing a new president in 1980 to replace the current military ruler, Gen. Francisco Morales Bermudez, but few Peruvians seem pleased with the road to democracy the government has chosen.

Within the military, a number of officials have reportedly objected to the gradual approach to elective government, and believe there should be no election at all, or an immediate presidential vote.

While the Popular Action Party spent the early part of this year in a whirlwind of campaign tours, its leader - and former national president - Fernando Belaunde Terry now says his party will "not legalize the assembly with our presence." The party withdrew from the elections, Belaunde said, because the government would not guarantee noninterference in the assembly' work.

Unlike the situation in other military-ruled South American countries, few Peruvians seem truly to despise their relatively mild-mannered military leaders, despite occasional exiles and imprisonments of apposition figures over the years. There is rather a feeling that the military, after all the promises and ballyhoo, has done very little.

"They're not bad people," said one bystander at the political rally, "They're well-intentioned. They're just bad at government."

The predominant political philosophy put forth by new military president, Gen. Juan Velasco Alvarado, was little different from that of Belaunde, the civilian president he deposed.

The military, however, was willing, and more able, to put into practice what Belaunde had merely set as distant goals. Its action was facilitated by dissolving the fractious Congress that had made Belaunde's task nearly impossible.

Expropriation of a number of foreign companies was followed by the establishment of diplomatic relations with the Soviet Union and other Eastern European countries. Communications were nationalized, workers were given part ownership in factories, and land was redistributed.

In the end, the military has been humbled, in part, by the very forces it sought to eliminate - an archaic social and economic structure that allowed reforms to reach only a fraction of the people, and the need for foreign money to keep the country running.

While many of the reforms remain, and the military has insisted that they be incorporated into the new constitution, the ruling generals and admirals are also leaving a record that is the dream of any politician looking to shoot holes in the incumbent.

"We have never believed that we have been perfect," President Morales Bermudez said in a recent interview. Counting off the successes of the "revolutionary government," he noted the "perhaps one of the most significant errors has been the lack of realism in the economic field."

Specifically, this translates into a $5 billion foreign debt, more than 40 percent inflation last year, foreign reserves in deficit by $1 billion and demands for higher wages. Workers who feel they have not gotten their fair share from the revolution, have staged crippling strikes.

At the same time, the military leaves an embarrassingly visible array of expensive white elephants - an elaborate new Ministry of Fisheries in Lima, for a coutry whose fishing industry has collapsed in recent years; arsenal of tanks, submarines and fighter planes that would serve a country twice Peru's size.

"We call that the Peruvian Pentagon," said an offical of Belaunde's Popular Action Party driving by the Ministry of War complex, an imposing a huge tower. The offical said Belaunde, a trained architect, described it as "miltary architecture - top-heavy.

"They started it five years ago and dedicated it last year," the official said. "We don't know how much it cost - its' a military secret."