The Soviet Union, which shot down a South Korean airliner last April after it strayed into Soviet airspace, has charged the Koreans about $100,000 for humanitarian aid to the 108 passengers and crew who survived the high-altitude attack and crash landing.

The bill, prepared several months ago, charges South Korean Airlines for food, medical help and transportation from the remote frozen lake where the pilot of the airliner managed to land after it was hit.

The Soviets, who refuse diplomatic recognition of South Korea, sent the bill to Pan American World Airways, which has acted as general representative for the Korean company here. A Pan American spokesman refused to comment but Senior Soviet diplomatic sources said the bill has not been paid.

Other sources said the Soviet authorities in their accounting "reserve the right for other charges not contemplated in the original bill."

One Western diplomatic source, informed of the Soviet action, said, "They Probably included the cost of the gas for the fighters and the machine gun bullets, too."

The Boeing 707 jetliner was intercepted by two Soviet fighters April 20 as it blundered over the strategic city of Murmansk, home port for the Soviet ballistic missile submarine fleet.

The fighters signaled the liner to land. When it ignored them, one interceptor fired on the plane with missiles after machine gun bullets were fired in warning across its nose. The attack, at 35,000 feet, punctured the passenger cabin, killing two and injuring ten. The 707 pilot, Kim Chang Kyu, dived the plane to lessen effects of decompression on the passengers and subsequently landed about 30 miles west of the small Soviet city of Kem on the defense-studded Kola peninsula.

Among the expense items listed by the Soviets were the cost of helicoptering the survivors from the wilderness landing site to Kem, three days of food and care there where they were confined to a town community center, bus rides to the city airport and the flight of two aeroflot jets from Kem to Murmansk with the passengers and baggage for eventual departure via a Pan Am 727.

South Korean Airlines' flight 902 had been en route from Paris to Seoul with a refueling stop in Anchorage, Alaska, when the Korean flight crew apparently became disoriented in the little-traveled airlanes near the North Pole and turned south toward the U.S.S.R. instead of continuing east to Alaska.

The Soviets at the time expressed concern that the plane was a disguised intelligence craft about to flee to safety in nearby Finland after probing the Murmansk defenses. Yesterday the Soviet diplomatic sources said their investigators, who detained the Korean pilot and navigator for a week of interrogation, have accepted that the intrusion was accidental.

As a gesture of friendship, they said, the Soviets released pilot Kim instead of jailing him for the three years prescribed in Soviet law for his actions.

The Koreans never have given a detailed explanation of how or why the aircrew became disoriented. It is widely thought here that inattention to the demanding requirements of transpolar navigation caused the plane to stray.

Meanwhile, the remains of the four-engine Boeing liner now rest on a small island in the middle of the lake. The Soviets dragged it there before the ice melted in the spring thaw. Informed Western sources said the Soviets have removed the tail and engines. They said the 707 apparently skewed sideways on landing, bending the engine pods out of line. The craft is said to be a complete loss. It is believed the Soviets eventually will dismantle it completely. They retail the cockpit recording devices which could help clear up the mysterious misfortune of flight 902.