It is a slow night at the Lonely Boy, a gay go-go bar in an alley of Bangkok's renowned Patpong red-light district. A barefoot youth dances in his underwear on a small, dimly lit stage next to a fountain at the back while three customers make conversation at the bar.

One of the waiters, Pisan, a hairdresser by day and a male prostitute by night, massages a customer's shoulders as he makes a pitch to "go upstairs." Then he is asked if he is not worried about getting AIDS, and a look of alarm crosses his face.

Yes, acquired immune deficiency syndrome is a big worry here, Pisan admits, and no, business has not been too good lately, but perhaps it will pick up when the tourist season hits full swing in December.

Such hopes may be forlorn. The AIDS scare is sweeping Asia.

Gay-bar owners here report that business is down by roughly a third, donations to blood banks are dropping, and the government is taking steps to bar foreigners with AIDS from entering the country.

Indeed, governments and individuals all over the region are expressing alarm about the deadly disease and seeking ways to prevent its spread into their countries. While the number of cases remains relatively small -- fewer than 70 deaths have been reported in the Asian and Pacific region, compared with 7,157 deaths reported in the United States -- some Draconian measures have been proposed to deal with the problem.

The reaction in many countries of the region may be out of proportion to the threat, but some health officials feel that this may not be such a bad thing.

"It's better to have a scare now and start protection measures and educate people," said Dr. Omsin Bulapadi, president of the Intensive Development of the Quality of Life Association, a Thai civic action group. "AIDS will be a very dangerous disease here if we don't start now."

The disease, which weakens the immune system and makes its victims susceptible to rare cancers and infections, is almost always fatal. There is no evidence that the AIDS virus is spread by casual contact with either victims or objects they have touched. It is believed to be transmitted through intimate contact with bodily fluids, primarily through sexual intercourse or the use of contaminated needles.

To date, homosexual men as well as intravenous drug abusers are at highest risk. There are also new concerns about spread into the heterosexual community, including contact with prostitutes. AIDS also can be spread through blood transfusions.

The worst affected country in the region appears to be Australia, where 52 AIDS-related deaths were reported and 118 persons were suffering from the disease as of mid-October. Estimates of the number of persons who have been exposed to the virus range from 20,000 to 50,000. Although Australia has only about 15 million inhabitants, its largest city, Sydney, has a high concentration of homosexuals.

To combat the disease, the conservative northern state of Queensland has set penalties of two years' imprisonment or fines of up to $10,000 for AIDS sufferers who knowingly pass on the disease sexually or through blood donations. The state of New South Wales also has drafted legislation to impose fines of $5,000 on carriers who knowingly transmit the disease.

Perhaps nowhere in Australia was the AIDS scare more evident than in the town of Gosford, north of Sydney. The city council there reacted with alarm this month when Eve, a 3-year-old with AIDS, bit her best friend, Lara. The two girls quickly made up, but the council banned Eve from kindergarten. Born prematurely, she had received the disease from blood transfusions.

Also relatively hard hit has been Japan, where at least 11 AIDS cases have been reported and scores of persons have tested positively for AIDS antibodies, indicating that they may be carriers. Some of them apparently received the virus from transfusions of contaminated blood products, and independent estimates indicate that thousands more Japanese also may have been exposed.

By contrast, China, with a population of more than 1 billion, has seen only one AIDS victim so far, an Argentine tourist who died in a Peking hospital in June. The case nevertheless had a strong impact in a country that has long considered itself immune from other societies' ills and where homosexuality is almost never publicly mentioned.

"Many people in society now have a terror of this disease," the official Shanghai Liberation Daily reported last month.

While some doctors feel the spread of the disease to Chinese citizens is almost inevitable, the newspaper said that "with serious prevention work, it is entirely possible that we can prevent the invasion of AIDS." The paper called for thorough health checks on persons and substances arriving in China and said traditional Chinese medicine might provide a cure.

The Chinese Health Ministry already has announced a ban on imports of nearly all blood products to prevent the spread of the disease through transfusions.

In Pakistan, health officials have started testing even imported used clothing.

Although the Pakistani Health Ministry pointed out that the virus cannot survive outside the body, several politicians and Islamic scholars demanded a ban on the clothing imports, worth about $25 million a year. Sellers of second-hand clothing charged that the local textile industry was behind the move.

The Islamabad government also has banned blood donations from its citizens who have lived abroad for more than three years but has rejected calls for blood tests on all arriving tourists.

In the Pakistani frontier town of Peshawar, an Afghan guerrilla leader appeared to show more concern about AIDS than the war ravaging his homeland when he demanded that U.S. relief volunteers and medical personnel working in Pakistan be screened for the disease.

So far, Pakistan has had one AIDS patient, a foreigner who recently left the country.

Fears that the disease will spread are especially acute in Asian countries whose appeal as tourist destinations is liberally spiced with sex.

In Thailand, which has about 500,000 female prostitutes -- and an unknown number of male prostitutes who cater to homosexuals -- government health authorities have begun a survey to test for AIDS in Bangkok's Patpong district and the beach resort of Pattaya. Both places are popular with foreigners.

According to Dr. Vinich Asavasena, the director of the Thai Health Ministry's department of communicable disease control, 3,000 prostitutes, including 500 males, who work at bars, discos, massage parlors and other establishments in the two areas will undergo blood tests this month. Those tested will receive booklets in which the results will be recorded. The booklets are already in use for women prostitutes to show they are free from the more common venereal diseases.

During the past year, Vinich said, Thailand has recorded six confirmed AIDS cases. All the victims were male homosexuals who acquired the disease from sexual activity, and all have died. Two were Thais, three were Americans and one a West German.

In addition, four persons in Thailand are now classified as "pre-AIDS" cases, and another 14 have tested positive for the disease in blood samples. Each group includes one woman. Six of the 18 are foreigners.

"We are afraid that if AIDS spreads to female prostitutes, it might spread to other Thai males," Vinich said. He said the Health Ministry has asked immigration authorities to deport foreigners with AIDS or bar them from entering Thailand. But he says it would not be feasible to administer blood tests to arriving visitors.

However, Omsin, the head of the Thai anti-AIDS civic action group, says that "if people appear gay, they should be tested for AIDS."

Some Thai officials feel private organizations like Omsin's may be doing too good a job in promoting awareness of AIDS. Public Health Minister Marut Bunnag recently warned the groups that their activities could hurt tourism.

In the Philippines, another country that has attracted foreign "sex tours," authorities this month reported their first known AIDS case, a middle-aged homosexual Filipino who had returned from the United States to die.

Singapore has registered at least five AIDS cases. All the victims are said to be homosexuals or transvestite prostitutes. The city-state has earmarked $900,000 a year to screen blood donors and keep blood banks AIDS-free.

In neighboring Malaysia, no AIDS cases have come to light yet, but the Moslem leadership has spoken out strongly on the disease. Prime Minister Mahathir Mohammed recently told a meeting of his ruling party that AIDS was God's way of punishing man for straying onto the wrong path.

In Indonesia, President Suharto has asked government agencies to inform the public about the disease, and the health minister has called for a crackdown on hotels and steam baths frequented by homosexuals.