AID workers in Hong Kong have been planning the next step in their fund-raising campaign to help the growing Rwandan refugee crisis. What happens in the next few days following yesterday's withdrawal of French troops will prove critical in determining just how much more aid will be needed. The onset of the rainy season has also increased the number of cases of malaria, sparking fears of widespread infection. ''The refugees are cold, wet and miserable, at prey not only to the elements but to the growing culture of violence in the camps,'' a Red Cross spokesman said. Relief workers fear that the withdrawal of the French could increase security problems, making the job of aiding the refugees that much more difficult. Yesterday, the Hong Kong Joint Appeal for Rwanda on behalf of the Red Cross, Oxfam and Medecins Sans Frontieres entered its fifth week with total donations reaching the $14 million mark. A new advertising campaign to increase awareness is planned for the territory, and children returning to school after the summer holidays may find they are learning about Rwanda as part of a new education programme. ''We will be closely watching what is happening in Rwanda this week as the situation reaches a very critical point. What we do next very much depends on how things develop,'' said Hong Kong Red Cross secretary-general Christine Fang Meng-sang.