DELISTING a company is the stock exchange's ultimate weapon - but one that can easily backfire. Hongkong Far East Credit and Properties - which seems to be unrelated to other companies listed in the territory with similar names - was one of the last two companies to be delisted in January 1990. The other was Sunstate Finance. Shareholders in Hongkong Far East seem to be left holding share certificates useful only as wallpaper. ''Every stock exchange has this problem,'' said exchange listing head Herbert Hui Ho-ming this week. ''How can shareholder interests be served by delisting a company? Innocent shareholders can be hit by this.'' Mr Hui said delisting a company was a last resort, and noted with satisfaction that no company had been delisted in his spell as head of the listing division. Since Hongkong Far East was delisted for not producing an annual report, all the directors have resigned, the company share register has disappeared and the flow of information to official sources, such as the company registrar, has dried up. Also, no one seems to know where the company's assets have gone. Shareholders in the company when it was listed remain, in theory, shareholders in a public but unlisted company. Mr K.R. Chatru is one. He bought 70,000 shares while Hongkong Far East was a thriving company in the 1980s, with some brokers tipping it as a growth firm due to logging and property interests, mostly in Thailand. In April 1991 he contacted the Financial Secretary's office, which informed him that ''we are looking into your concerns and shall revert to you shortly''. He has heard nothing since. The company was suspended in May 1988 when its controlling shareholder, Monab Nominees, said it had not received dividend payments for three years. It was delisted less than two years later, after the exchange said the company had failed to respond to questions about its financial data. The last remaining directors resigned in August 1992, according to company records. One of the ex-directors, Kiang Wing-che, said last week that most had gone to Canada, and that he now had no connection with the company. The company's registered address is now occupied by Maxsuper Realty, a property company which says it has no relationship with Hongkong Far East. Mr Arthur Yuen, an assistant secretary with the Government's Financial Services branch - formerly Monetary Affairs - said: ''We don't know what's happening with the company. ''But the company is still on the register so it still 'exists','' he said. When a company is taken off the stock exchange, the status of shareholders is in theory unchanged, Mr Hui notes. But the withdrawal of an effective market means they are locked into the company, with no means of withdrawing their capital. Brokers sometimes make a market on a matched-bargain basis if there is a special reason. For instance, a few brokers are prepared to keep tabs on willing buyers and sellers to create some kind of market in a company called Special Assets Ltd, which was spun off from another listed company as a holding vehicle for some assets that were difficult to realise. But it seems unlikely that brokers would be interested in a company delisted for not following exchange rules. Once off the exchange, neither the exchange nor the Securities and Futures Commission has a role in regulating the company's affairs. And once the spotlight goes off a company, there is no incentive to keep its paperwork at the companies registry up to date. Officials there say they act only if there is a complaint, when they chase the directors of private companies through the courts for statutory returns. The last annual return on file from Hongkong Far East is dated 1988. Hongkong Far East directors were taken to court in 1989 and fined $3,200, but no action has been taken since. The responsibility for regulation is now with the Financial Services Branch, which is having another look at the company.