A setback, for now, for SE Asian pirates

A bit of gamesmanship between Indonesia and Singapore has, at least temporarily, halted attacks by armed pirates on oil tankers and cargo vessels navigating a narrow waterway near Singapore.

The attacks had embarrassed both countries, alarmed some international shippers, and sparked a host of proposals for improving security aboard ship.

So, with the arrest of five alleged culprits by Indonesia, there is a tentative sigh of relief.

In the past two years at least 40 large tankers and container ships have been attacked by pirates in the narrow Phillips Channel, a continuation of the Malacca Strait.

Piracy is a sensitive subject between the two Southeast Asian neighbors.

While Singapore was pointedly referring shipowners to Indonesia as the party responsible for dealing with piracy, Jakarta authorities suddenly claimed they had arrested five people on islands near the Phillips Channel.

According to Indonesia, the men are Chinese-speaking and have been operating from a hideout at Pasir Panjang on the western edge of Singapore.

The implication that Singapore has been harboring a nest of pirates is not taken seriously by local shipowners. Many of these believe the culprits were off-duty Indonesian marines, operating from the many outlying islands close to the Malacca Strait.

But worldwide publicity given recent pirate attacks clearly embarrassed Jakarta and caused the authorities there to order some action to be taken. The alleged pirates have not been identified since they were arrested in October. But attacks on ships in the Phillips Channel have stopped.

Owners and crews are relaxing - slightly. But no one is yet confident that the problem has been solved. Many believe that the ''pirates'' are lying low until the heat is off.

The raids had come to light only in August when shipowners in Singapore and London lifted a self-imposed news blackout to get the authorities in Singapore and Indonesia to do something about the piracy.

The five-mile-long Phillips Channel is in Indonesian waters but ships entering Singapore Harbor - one of the world's biggest ports - have to navigate it.

In what appeared to be well-planned attacks, small groups of men in fast boats drew alongside ships slowing to circumvent a navigation buoy in the channel, usually after midnight when a minimal watch was being kept.

Using grappling hooks, the pirates boarded the vessels and headed for the master's cabin where they demanded assorted booty, often including the crew's wages as well as radios, watches, and cameras. Crews involved reported that the men were usually wearing swimming trunks and carrying military-style webbing belts with knives.

The ships that fell victim to the pirates this year included the Shell-chartered tanker, Mammoth Monarch; a Mobil tanker, Corsicana; and a BP tanker, British Beach. At least 11 Japanese vessels were raided by pirates in the second half of 1981. Such tankers are easy prey for marauders because they travel more slowly than cargo vessels, partly to conserve fuel. They also tend to have smaller crews.

No one was seriously injured in any of the incidents but the master of one ship was briefly hospitalized after being manhandled.

While the Singaporean and Indonesian authorities disputed jurisdiction, several solutions were proposed by the shipowners themselves, ranging from the sensible proposal that crews keep searchlights in play after midnight and arm themselves with high-velocity water hoses, to the less conventional - the enlistment aboard ship of ''lean and hungry'' Doberman pinscher dogs. (Unfortunately the dogs were adopted as pets by the crew and apparently lost their fighting spirit).

Several security firms offered their services, including an Australian company, Arpad, which employs former special air service personnel from Britain, Australia, and Zimbabwe. Arpad's plan was believed to include the use of specially trained commandos, using low-velocity weapons, to arrest the pirates. However, this proved a little too much for the Singapore authorities who failed to give the Australians the go-ahead.

Mobil enlisted the services of a local security firm, Cisco, to patrol around VLCCs (very large crude carriers) discharging oil in Singapore refineries or at anchor.

But some shipowners saw the dangers of employing armed guards on the vessels themselves. With such a highly inflammable cargo on board, any exchange of fire could spark off a major explosion.