HONG KONG people are being urged to sign organ donation cards as part of the ''Gift of Life'' campaign to try to save the 1,000-plus people who die each year while waiting for life-saving transplants. Dr Mok Chiu-yau, senior medical and health officer of the Department of Health's central health education unit, said about 1,000 kidney patients were dying each year because of the lack of organ donors. Kidney disease was the number six killer in Hong Kong, he said. Other patients were exposing themselves to the risks of organ donations overseas, where operating standards were not always satisfactory. And if countries did not screen their donors, Hong Kong patients also risked picking up blood-born diseases, such as AIDS or hepatitis B, he said. ''As far as I know, most of these donors are executed criminals,'' Dr Mok said, referring to China, a popular source of kidney transplants among Hong Kong patients. He said patients waiting for other transplants were in an equally serious position. Dr Mok said surveys showed 30 per cent of Hong Kong adults were willing to donate their organs after death, but only about two per cent carried an organ donation card. ''If we can at least double this, we would be very happy,'' he said. The highlight of the campaign is an exhibition at Metroplaza in Kwai Fong this weekend. The Lion Rock Jaycees hope to attract 10,000 people to the event and to have 1,000 of them sign cards on the spot. Kidney donations had crept up by only a handful each year, from 18 in 1988 to 34 in 1992.