AS THE Hongkong Repertory Company prepares to open its 1993-94 season with a production of Shakespeare's King Lear, scores of smaller amateur and professional groups are crowding on to the territory's stages, expanding and redefining the theatrical scene. The Rep hopes to take its show, which will be produced in both Cantonese and Mandarin, to Taiwan, China and Singapore. Daniel Yang, artistic director, said his Lear would be every inch an ''international-standard'' show. As if to confirm this he has brought in one of China's top actors, Hu Qingshu, to star in the lead role in the Mandarin version. Also imported are his American costume and scenery designers. Yang said the production, which opens on May 15 and is based on his own translation, would be in the grand, classical tradition. At the other end of the spectrum, Yang's vision of ''classical, grand-style'' Shakespeare is being challenged in English by a small, women's company called Agitprop, which made its debut at the 1993 Fringe Festival. Its new production, A Ladies' MacBeth, runs from May 12-15 at the Arts Centre's Macauley Studio. Written by Agitprop's artistic director, Emma Griffiths, A Ladies' MacBeth is ''a collage of new scenes using the original language'', which features an all-woman cast. ''We're trying to look at the power of evil, the struggle of politics and issues of how we define gender,'' said Griffiths. She explained that her idea for single-sex casting came from Shakespeare himself: all of his actors were men. Between the two poles represented by classicist Yang and revisionist Griffiths lies a burgeoning expanse of Western and Chinese, traditional and contemporary, and adult and children's theatre. The Chung Ying Theatre Company will open its 1993-94 season this month with Studio Shorts II. At the end of the month the group will travel to Canada to take part in the Vancouver Children's Festival and perform in Calgary and Saskatoon. Until recently, Chung Ying and the Hongkong Rep were the only full-time companies, but the number of professional drama companies in the territory will have doubled by the end of the year. After a decade in existence, the Exploration Company has qualified for a $3.5-million general support grant from the Government's cultural funding body, allowing it to support its theatre full time. And by September, the Sha Tin Theatre Company expects to form a professional group to be known as Prospect. Meanwhile, the long-established English-language American Community Theatre will perform Tennessee Williams' Night of the Iguana (May 20-29 at the Arts Centre's Shouson Theatre) and Terence McNally's Frankie and Johnny in the Claire de Lune (June 6-12 atthe MacCauley Studio). The small amateur group Not So Loud recently finished a short run of Chicken Wing, an original play which focused on the Vietnamese detention camps. The only group writing its own full-length dramas in English, Not So Loud ''tries to be humorous and serious at the same time'', according to creative director Tom Hope. Amateur Cantonese theatre has also expanded in recent years, but it is not clear whether audiences' demands for new dramatic productions can match the growing supply of young theatrical talent clamouring to perform. Some critics, such as Cheung Fai, editor of arts magazine Crossover, think the only trend among these small groups is imitation and repetition. But Yang said things were not so dire. Although he admitted Hongkong hadn't produced its own voice and didn't have any major playwrights, he said theatre here had come a long way in a relatively short time. ''Don't forget, we got off to a late start. Fifteen years ago there was no repertory company here, and as recent as eight years ago there was no major training ground for actors. We should be very proud of what we've achieved.''