The Panamanian government quietly exulted today in yesterday's two-to-one margin of approval in a plebiscite on the treaties that will turn the Panama Canal over to this country.

On the other side off the fence that separates Panama from the U.S. controlled Canal Zone. American mothers of a Veterans Day ceremony solemnly told their children that it may be the last parade they see here.

All but a small fraction of the vote had been counted by early this morning, showing that close to 470,000 voters approved the treaties, with almost 230,000 opposed.

"I had no doubt that it was going to happen this way," Panamanian leader Gen. Omar Torrijos said last night, "because I knew that our people would not turn their backs on the country when the country demands their presence."

More significant than large turnout, however, was the number of "no" votes which, fo rdifferent reasons, surprised both proponents and opponents of the treaties.

Opposition leaders charged that the figures, easily divided into a two-to-one approval majority in many of the country's most populous voting district, were too unrealistic to be genuine.

"We always thought the govenment would make it two-thirds," said one opposition source, "because that's what's needed in the U.S. Senate" for treat ratification. The Panamanian government, he said, "wouldn't want to look too much worse, or much better."

The opposition, primarily Panamanian intellectuals and leftist students, said their private polling showed treaty opinion split almost down the middle in Panama City, where the vote was tallied at about 235,000 to 120,000 in favor of the treaty.

They had maintained that as much as opposition to the treaties, the vote would reflect opposition to the military-run government here, which took power in a 1968 said.

During the month before the plebiscite, the Torrijos government predicted 85 to 90 per cent approval of the treaties, but government sources today said they were not troubled by a stronger opposition showing.

An overwhelming "yes" vote, said one source close to Torrijos, could have fueled the treaty opposition fire in the United States.

"They would think there must be something wrong with the treaties, if the Panamanians think they are so good."

A larger pro-treaty vote, he said, would also have increased accusations of election fraud both here and abroad.

Under the two treaties signed by Torrijos and President Carter Sept. 87, operation of the canal will be gradually turned over to Panama, with the changeover to be completed by the year 2000. The United States, however, will retain a permanent right to defend the canal and to send a priority basis.

While the treaties still face difficult passage through the U.S. Senate, the Panamanian government believes strong approval here will improve their chances in Washington.

Despite opposition accusations there has been only one definite case of fraud reported in yesterday's plebiscite. Juan Carlos Voloj, an opposition school teacher, allegedly voted "no" eight times under his own name to show that government registration procedures were inadequate. To prove his point. Voloj demonstrated to a cameria crew that he had voted twice at one polling station and had them film the two signatures.

Government election officials said that the names of all voted would be fed into a computer to check for duplication.

While most Panamanians expressed subdued pleasure over the outcome of the vote, at least one group showed its disapproval. In one village on the San Blas island off Panama's Caribbean coast yesterday, members of the Cuna Indian tribe, many of whom work in service jobs in the Canal Zone lowered the Panamanian falg and raised the U.S. Stars and Stripes.

In the Canal Zone itself, the mood was one of resignation. While the American Legion, the Shriners, and local for the morning parade, piles of hamburgers and hot dogs at the Veterans Day picnic uneaten.

"We've blasted Congress with all the information we've had since 1957," said Ed Kennard, a retired Canal Zone Company employee and American Legion memer. "What more can we do?"