ALTHOUGH usually regarded as a property company, over recent weeks Cheung Kong Holdings' role as an investment holding company has come to the fore. This is thanks to its acquisition of stakes in three companies being used as back-door listings by mainland companies, sometimes in association with its 50 per-cent owned CEF Holdings. The sprawling empire of Mr Li Ka-shing's Cheung Kong has equity stakes or convertible notes in more than 20 Hongkong listed companies. Together with their own listed subsidiaries' subsidiaries, they make up more than 10 per cent of companies on the Hongkong market. ''Property is still the mainstay, but it's becoming more and more an investment holding company and project management company,'' said Mr Terence Chan Tai-yin, analyst for HG Asia. In 1991 and 1992 the company expanded its presence in the Hongkong stock market with a series of convertible notes, mostly to smaller companies with some China connection, which could be converted to equity at a later date at a price fixed at the time ofissue. The purchases were generally well-received by analysts, who reckoned it was a good way to channel cash flow and better than funding some adventure elsewhere in the world, where its record has been sometimes less than impressive. A Vickers Ballas report issued late last month says its investment portfolio has a market value of about $6.8 billion, which is 44 per cent above its book cost. The largest is its long-held stake in Hopewell Holdings, which is worth more than $1 billion. The spending on convertible notes died down last summer - but now its list of associates is expanding once again. Last week it helped take control of Kader Investment in a consortium led by Shougang, the acquisitive mainland steelmaker held up as a model of management excellence by Chinese patriarch Deng Xiaoping. With Shougang it has also taken stakes in Santai Manufacturing and Tung Wing Steel. This comes on top of Mr Li's aim, stated last week, of increasing Cheung Kong's stake in Hutchison to 42 per cent, the level it stood at before conversion of the Polycourt warrant it issued. Analysts say the moves in association with the mainland concerns represents a new phase in the company's development, although it is a technique that it has tried successfully before when it helped build the China-controlled trading hong CITIC Pacific. ''With asset injections these things are going to be mini-CITICs or even CITICs,'' Mr Chan said. Vickers Ballas associate director Adrian Ngan Wai-hung said: ''Cheung Kong will play a role in providing financing, investment and business connections in Hongkong. ''Cheung Kong is nurturing these red chips.'' The cost of buying into these shell companies is comparatively small. The real cost comes when assets are injected. If the stake is not to be diluted then a substantial cash injection may be needed. In the case of Tung Wing Steel, the cost of subscribing to the $1.88 billion rights issue announced on May 10 will be more than four times the initial investment. If Cheung Kong is to retain stakes in the red chips it is nurturing, where will the cash come from, given the cash demands from its property business? Analysts are divided. One possibility would simply be a cash call. But there are more complex transactions that could be constructed based around the convertible notes. The convertible notes could be redeemed instead of taking the shares. The note issued to Evergo is being redeemed with a six-month extension and the stake of a few per cent in the company was sold in the open market. The redemption of the note means Evergo must hand over more than $550 million at the end of June. However, a wholesale redemption would lose the substantial paper profits to be made by converting into shares thanks to the big price rises posted by some of the companies. Mr Ngan says the notes or converted stakes could be injected into the new red chips the company is helping create. The increasing size of the group's investment in the Hongkong stock market makes for additional problems for analysts covering the company. Like all companies, the group is bound by the disclosure ordinance that took effect in September 1991 which means all substantial shareholdings, defined as more than 10 per cent, must be declared, and any change of more than one percentage point also declared. However, Mr Chan said tracking the cost could be very difficult, particularly for shares bought on the open market. In addition, it is difficult to guess how long the growing red chips will stay under Mr Li's watchful gaze. After just seven months, Santai already is being sold to Tung Wing Steel. Cheung Kong's recently-issued annual report does not help. It states: ''The directors are of the opinion that a complete list of the particulars of all associated companies will be of excessive length'' and it names only those companies which ''principally affect the results or assets of the group''. The only Hongkong-listed company recorded is Hutchison Whampoa.