THERE is talk that Miss Saigon, Lea Salonga, might be heading this way soon with an all-Filipino stage production of My Fair Lady - the film having already been given a prominent revival by TVB last month. Salonga, who was discovered by multi-millionaire British impresario Cameron Mackintosh for the title role of Miss Saigon both in London's West End and New York's Broadway - her phenomenal success in the part won her almost every major theatrical award going - is rehearsing as Eliza Doolittle for the Manila staging which takes place later this month. But, according to our sources, if Salonga can be freed from some of her other contractual commitments, then there are some financial backers in Hong Kong who are keen to bring the production here. Ironically, one of the commitments she has to fulfil soon after the Manila run of My Fair Lady is a promotional tour for her new album of romantic ballads (her first album since signing up with New York based Atlantic Records) which might bring her to Hong Kong anyway. Talking to Keeping Posted, Salonga - who lists shopping as one of her hobbies which should make Hong Kong her kind of town - told us that she was still awaiting news as to how the plan to bring My Fair Lady here will work out. ''It will be very good if we could,'' she said, ''but there will be a number of matters to be ironed out first.'' These days Salonga is much in demand both for stage and film roles. But, as she told us with unnerving modesty: ''I am very selective about the roles I choose because I know my limitations. For example, I've decided that the part of Evita is not for me because I feel I am too young to play that role.'' As a gesture of gratitude to the Philippines Repertory, which has been a happy casting ground for his productions, Mackintosh allowed it to stage its own production of the block-buster musical, Les Miserables in October. We understand that plans also to bring that production to Hong Kong were thwarted by Mackintosh's insistence that it should be put on only in Manila so as not to clash with the impresario's forthcoming Asian staging of Les Miz in Singapore.