THE family of a 22-year-old Hong Kong labourer will be waiting at Changi prison in Singapore this morning for word that last-minute international appeals to stop his execution were successful. Fung Yuk-shing was scheduled to be hanged today for drug trafficking. Amnesty International began an urgent appeal yesterday, asking thousands of supporters throughout the world to send faxes to Singapore President Ong Teng Cheong, urging clemency. Last night, an Amnesty spokesman in London said they had not heard of any new developments and conceded that clemency was rare, although not impossible. An Amnesty spokesman in Hong Kong, Robyn Kilpatrick, said: ''[Fung's] only hope is if President Ong commutes his sentence at the last minute.'' She said there were very few incidents of clemency in Singapore, where anyone found guilty of holding more than 15 grams of heroin is automatically in line to be hanged. Fung, a casual labourer, was arrested on November 21, 1990, at Changi airport with 2.78 kilograms of diamorphine, a grade of heroin, strapped to his body in 16 slabs. He was sentenced on December 5, 1992, to be executed, although he claimed he did not know the precise nature of the substance he was carrying. A final appeal for clemency, lodged by his lawyer last December, was turned down last month. Several members of Fung's immediate family have been in Singapore all week to visit him as the date of his execution approached. A spokesman for the Immigration Department said it had been in contact with the British High Commission in Singapore for the past three years over Fung's case. It had also kept in close touch with members of Fung's family. ''Singapore authorities hold the view that any relaxation of their policy would be seen as a weakening of their fight against international drug trafficking.'' A spokesman at Government House said Governor Chris Patten would not appeal on Fung's behalf, although he, with the Hong Kong Government, backed a request made by the British Foreign Office to commute the death sentence. The head of consular affairs at the British High Commission, John McDonnell, was not available for comment as he was attending meetings at Changi prison all day. The public relations officer at Changi prison, where Fung has been held since 1990, said that she was unable to confirm whether Fung would be hanged this morning. She said that while there were several prisoners scheduled to be executed, she did not know whether Fung was among them.