Scratchy music blares from loudspeakers set up by sidewalk hawkers in Bangkok, a noisy come-on calling foreign tourists to huge displays of music cassettes offering everything from Paula Abdul to Coleman Hawkins. The tapes are priced at just $1 each.

"You want to hear first?" one hawker asks a hesitant woman. Not waiting for an answer, he tears off the cellophane wrapper and pops the tape into a boombox. The tourist nods her assent and grabs a few extra cassettes to buy. A few paces down the road, another hawker tries to lure customers to buy videocassettes that contain first-run movies -- $8 buys a copy of "Teenage Mutant Ninja Turtles."

Both hawkers operate outlets for a booming industry in Thailand: the pirating of foreign "intellectual property." Elsewhere in the city shoppers can find store after store with fake Gucci handbags and Izod shirts, as well as copied computer software and foreign-developed pharmaceuticals.

Yesterday, a group that includes trade associations of the U.S. film, music and software industries notified the Thailand Embassy in Washington that it will file a formal trade complaint against Thailand Nov. 15 unless prosecution of specific alleged pirates occurs in the meantime. The complaint could result in the United States imposing trade sanctions against Thailand.

Thai officials said they are addressing the problem, but that the job is not easy. "We are working on a new law to improve the enforcement as well as to extend the coverage," Thailand Ambassador Vitthya Vejjajiva said yesterday.

American companies are not willing to wait. Foreign piracy was once just a nuisance for the U.S. economy. But as its manufacturing competitiveness has eroded and its trade deficit has climbed to more than $100 billion a year, U.S. government and industry have moved to protect intellectual property, which tends to center on sectors in which U.S. exports remain strong. Piracy reduces those exports, however, by displacing U.S. sales.

Washington now is trying to get the General Agreement on Tariffs and Trade (GATT), the Geneva-based group that polices world trade, to cover intellectual property as well. Vitthya said Thailand is waiting to see how those deliberations are concluded, so that the country's law will accommodate GATT policies.

According to the Motion Picture Association of America, exports of films, videos and TV programs earn the United States about $3 billion annually. "This is probably the single most wanted United States export ... ," said Jack Valenti, the association's president. "No matter how successful the Japanese or Germans are, they cannot clone or develop this American trade asset."

Valenti said members of his association had sales of $5.1 million in Thailand in 1989. But about 80 percent of the home video market there is sales of pirated material, he said. "We ought to be doing at least $15-plus million in Thailand," he said. Valenti's association is part of the International Intellectual Property Alliance, the group threatening the complaint.

Many people in developing countries view piracy as a harmless and low-cost means of transferring a bit of the wealth, learning and glamour of the industrialized world to their own backyard. Legitimate copies of items in question would be too expensive for ordinary people to afford, they said, so sales lost by foreign companies are not really so high.

Governments that do want to crackdown on piracy often do so only cautiously, as it may raise prices and create an impression of knuckling under to foreign pressure. Nonetheless, in the 1980s, the United States reached agreements with Japan, South Korea and Taiwan that reined in piracy considerably in those nations.

Thailand's critics said authorities there sometimes will not act unless paid "incentives" and when they do, may be bought off by the other side. Pirates who do end up in court may be fined only a fraction of what they are making, so they continue in business.

Historically, large-scale piracy has occured most often in poorer countries, including in the United States in the last century, many experts said. But as countries grow wealthier, they begin enforcing property rights, as their own citizens are increasingly the ones holding them.

Thailand already has a thriving pop music scene and some people in it, such as music company president Rewat Buddhinan, find they are hurt as well by piracy. "Nothing's really going to change until we get stricter laws on the books," Buddhinan said, "and {until} the government is willing to enforce them." Special correspondent Mary Kay Magistad in Bangkok contributed to this report.