IN THE goldfish bowl that is Hong Kong, Dr Edgar Cheng Wai-kin has been supremely successful in maintaining a low, if not invisible, profile. Six years after returning to the territory from the US the man who heads up the private investment empire of the family of the late Sir Y. K. Pao remains a little-known figure in the territory's clubby corporate world. It is just the way he likes it. But from November this year, Dr Cheng's cover is likely to be blown. Although the news is not yet confirmed he is, in racing parlance, a ''sure thing'' to become the new chairman of the Stock Exchange of Hong Kong. Barring incident, the 50-year-old doctor-turned-businessman and now Beijing adviser will replace Charles Lee Yeh-kwong at the helm of the exchange in the lead-up to the territory's handover. Paradoxically, it is his virtual anonymity in the broader corporate world of Hong Kong that has helped make Dr Cheng such an attractive candidate. ''He is very low-profile. He is involved in private business and there are no obvious conflicts of interest. He would appear to be very acceptable to all members of the [stock exchange] council,'' said Howard Gorges, of the brokerage South China Research. ''He has also been on the council for a while and is well qualified for the job.'' The eldest of five brothers, including former Wharf executive director Edward, Edgar Cheng left Hong Kong to study medicine in the 1960s, becoming an associate professor of medicine at Cornell University in New York. In the US he married Doreen Pao, youngest daughter of the late shipping magnate Sir Y. K. Pao, and it was the offer of managing director of Sir Y. K.'s Worldwide Investment - the private investment arm of the Pao family empire - that eventually lured him back to Hong Kong. Estimates are sketchy but the last reported value of Worldwide Investment was about US$1 billion, invested mainly offshore. Dr Cheng has since quietly divided his time between Worldwide and his own family's burgeoning business interests. The Chengs, who hail from the same part of China as the Pao family, have established themselves as one of the pre-eminent Hong Kong families based in Singapore. ''They endeared themselves to the Singapore Government as virtually the first Hong Kong family to invest in the island state,'' says one analyst. The family-controlled Singapore listed company Wing Tai has developed extensive property interests in the city, while in Hong Kong USI (Holdings) controls a large garment operation. Edgar remains as non-executive chairman of Wing Tai and has been closely involved in the group's recent expansion into China infrastructure plays. In a notable coup for the family, Wing Tai stitched together an ambitious joint venture with the Singaporean Government and Worldwide Investment to develop a virtual new town in the city of Ningbo, south of Shanghai. The family's Hong Kong operations revolve mainly around the traditional roots of garments with the listed USI (Holdings) manufacturing clothes in the territory, Hong Kong and Malaysia with markets in Asia and London. USI is chaired by brother Christopher with youngest brother Edward, who left Wharf last month, recently being appointed chief executive. Of the two remaining brothers, one, Wai Keung, is chief executive of Wing Tai in Singapore and the other, Edmund, is a civil engineer and architect and board chairman of Singapore's tourist bureau. Apart from Wing Tai and Worldwide, Edgar is also vice-chairman of the Hang Seng Bank and a director of two funds. One story has it that when his appointment at the bank was announced, several senior staffers were caught by surprise, never having heard of the new man. Outside business, Dr Cheng has been appointed a Hong Kong affairs adviser to Beijing and is a director of the One Country, Two Systems Economic Research Institute, a privately funded body that looks into economic issues arising from the territory's return to Chinese rule. One academic who has been involved with the institute and has met Dr Cheng described him as a ''thoroughly likable'' person, although he appeared to be uncomfortable with a higher profile. ''I am very surprised he has been chosen. He does not seem like a person who enjoys being in the spotlight,'' he said. However, after the shake-up following the 1987 stock market crash, and the successful listing of the first batch of the China ''H'' shares, the role of chairman may not require such a high profile, according to Mr Gorges. ''The reforms and the modernisations are in place; the next chairman will probably be able to be more low-key because a lot of issues have been dealt with. It could be more of a 'steady as she goes' role,'' he added. Whatever the role there is little doubt that Dr Cheng will be propelled into the mainstream of Hong Kong Inc as never before, and that the territory is going to be hearing much more about him and from him.