Fear of the 1997 Chinese takeover of Hong Kong has sent a flood of Asian investment into Chinese-American communities, according to California merchants and police officials, creating new opportunities for both legitimate businesses and a new breed of criminal gangs.

In Asian-immigrant meccas such as San Francisco, Los Angeles and this eastern Los Angeles County suburb, rising commercial property rents and new Chinese-character signs on the streets indicate that a boom is in progress, clouded by concern over what money escaping from Hong Kong might bring with it.

Community leaders such as Lily Lee Chen, a Monterey Park City Council member, argue that "Asian Americans are being singled out" for crime problems that all communities encounter.

But Inspector John McKenna, head of the San Francisco police task force on gangs, said his recent trip to Hong Kong and talks with police officials there convinced him that "a lot of money is coming into the United States," some of which is falling into the hands of Asian groups devoted to extortion and drug trading.

The new crime threat, if it exists, is so new and so difficult to detect that U.S. government agencies appear to disagree on its progress.

Attorney General William French Smith told the President's Commission on Organized Crime that, because "Hong Kong will become part of mainland China in 1997 . . . , there is now occurring an exodus of criminal Triad Societies' assets into other parts of the world . . . . "

But a State Department official said he had no indication of an increased flow of money or people out of the British territory.

A string of murders and reports of intimidation of merchants and drug transactions in West Coast communities have drawn little attention, in large part, police officials say, because nearly all the victims have been Asian immigrants.

Often, the crimes are not reported at all because the victims are frightened, do not understand U.S. law and are accustomed to traditional Asian avoidance of police.

Crimes that do not directly affect the non-Asian community receive little press notice. And an experienced eye is often needed to see the potential for crime in what otherwise appears to be a healthy business climate.

Monterey Park Police Chief Jon Elder, advising the presidential commission on his city's abundance of new banks, noted the oddity of having 28 different banks, not counting branches, in a community of 58,000 people.

"It is suspected that money-laundering is a featured specialty of these banks," said Elder, according to a version of his remarks released by the commission.

"The growth of these banks has been so fast that it is very difficult to keep track of them, let alone monitor any illegal activity in which they engage," he said. "Banks have sprouted up to replace gas stations, veterinary hospitals, hardware stores, restaurants and all other variety of businesses."

Gregory Tse, a realtor, banker and Hong Kong immigrant who is president of the Monterey Park Chamber of Commerce, acknowledged that the banking explosion shows "a lot of money coming in."

But he denied that the banks were laundering funds illegally and said the reports of gang activity were "exaggerated."

And none of the chamber members, as far as he knows, he said, are paying protection money.

It is a measure of how close the Asian and American communities have become that the British agreement to cede Hong Kong to Chinese control in 1997 has created such comment and controversy in California.

The Chinese have promised to leave Hong Kong's economic and social system untouched for 50 years, but the territory's criminal Triad gangs, involved in extortion and heroin traffic, appear unconvinced.

James D. Harmon Jr., executive director and chief counsel of the president's commission, said the Communists "pose a threat to the 80,000 or so Triad members." He said the commission "has uncovered evidence that some heroin-money-laundering operations are already being displaced from Hong Kong.

"Although the Triads now are op erational in this country, future events could pose the risk of a migration of entire criminal organizations to this and other countries."

A statement by a commission staff investigator said one Triad leader, former Hong Kong police detective Eddie Chan, headed a financial group being investigated in "three North American cities" for selling phony commodity contracts.

California police say most murders charged to Asian gang members are part of inter-gang warfare, the Taiwan-based Bamboo gang fighting the Viet Ching group of Vietnamese immigrants, and the Taiwan-based "Taitu" shooting at the Hong Kong-connected "Wah Ching."

Some killings may be political, however. Daly City police have suggested that the murder of Chinese-American journalist Henry Liu, attributed to members of the Bamboo gang, may have been motivated by Liu's attacks on the Taiwan government.

An anticommunist Vietnamese group took credit for the San Francisco shooting of Van Luy Nguyen, 71, a long-time Hanoi supporter, and the murder of Nguyen's wife.

Many police departments in large Asian-American communities have hired officers who speak Asian languages to help detect gang crimes and win resident cooperation in identifying gang members.

With his special task force, concentrating almost exclusively on Asian gangs, McKenna said, "we have it fairly well under control, but we have not stopped it. It is still going on."