A Thai court today gave former Special Forces officer James G. (Bo) Gritz and four associates suspended one-year jail sentences and fines totaling $680 for offenses related to forays into neighboring Laos to search for Vietnam-era American prisoners of war.

Gritz, 44, and his team later headed to Bangkok, where they planned to board a flight to the United States.

The five Americans each pleaded guilty to charges of possessing illegal radio equipment at a rented house in this northeastern Thai border town beside the Mekong River that served as a base for a series of missions deep into the Laotian jungle. The charges carried maximum penalties of five years' imprisonment.

The Americans appeared relieved after hearing the verdict, but Gritz indicated he intended to continue the search that has occupied him for the past four years.

"With each ending comes a new beginning," Gritz said. "God save the missing in action. They need our help now." Nevertheless, the Thai court's decision appeared to bring down the curtain on Gritz's four-month run of what a Pentagon spokesman has called "guerrilla theater."

During that time, the escapades of the former Green Beret lieutenant colonel and his crew have combined elements of drama, deadly derring-do and opera bouffe.

The publicity surrounding Gritz's armed raids into Laos has embarrassed the Reagan administration, which is pursuing negotiations to account for the 2,500 U.S. servicemen still listed as missing in action in Indochina.

The would-be rescue operations started last November when members of Gritz's team arrived in Nakhon Phanom posing as Boy Scout officials. One was reported captured and later ransomed by a rival anticommunist guerrilla group in an abortive raid begun Nov. 27. But none of the Americans was injured until earlier this week when one of them jumped off a nightclub stage and twisted his knee after renditions of such songs as "The Ballad of the Green Berets."

After the failed November raid, Gritz and his team of former Special Forces comrades and anticommunist Laotian guerrillas reportedly went back across the Mekong to look for lost equipment and began planning another, larger, raid.

On Feb. 13, Thai police arrested two associates at the rented house, where they found the radio equipment and some commando gear. Gritz, who had vanished around Jan. 30, reappeared and surrendered to Thai police, saying the radio equipment was his. He was followed within a week by two other associates.

Gritz has refused to confirm earlier reports that he was on another raid in Laos during February, but he has hinted this repeatedly and has claimed to have acquired evidence that U.S. POWs are still being held.

The cast of characters in the various episodes has included, in addition to the highly decorated Vietnam veteran Gritz:

Scott Weekly, 36, a trim, intense-looking former Navy officer who served in Vietnam and earned the nickname "Dr. Death" for his expertise in various kinds of weapons.

Gary Goldman, 42, a former Special Forces comrade of Gritz who participated in the November raid.

Lance Trimmer, 43, a somewhat out-of-shape former Special Forces radio operator who maintained communications with Gritz from the rented house here.

Lynn Standerwick, 25, a shy woman whose father was an Air Force pilot shot down over Laos in 1971 and who also helped with communications at the rented house.

The defendants' lawyer, Ruen Na Phatthalung, said everybody "feels sorry for what happened and will never do it again."

Before Gritz appeared in court, however, he had insisted he still intends to see his task through. "It's over when the work is done," he adding, "If anybody else is going to pick up the baton, I'm ready to pass it off to anyone who's ready to take it."

Meanwhile, he said, he plans to return to the United States, where he says he faces an investigation by the FBI into possible violations of the Neutrality Act and regulations on the export of high-technology equipment.

Gritz said he remains "firmly convinced beyond a reasonable doubt that there are more than 10 American POWs still in Laos."

"What are 10 men worth?" he asked. "In Teddy Roosevelt's day they probably would have mobilized to come over here for one person." In an interview, Gritz reacted angrily to suggestions that he was stirring false hopes among the families of the missing in action.

"We're not doing this for the MIA families," he said. "We're doing it for our comrades, for our country and for our armed forces. Because it needs to be done. Because it's right. Now there's no excuse for people to say they don't know about the issue."