OUR best wishes will be with Dame Kiri Te Kanawa tonight as she sings at the Cultural Centre after fighting off a bout of flu that kept her in her Regent Hotel room at the weekend. We won't be there in person, as, like most of her other concerts in this three-week Asian tour, the single Hong Kong date has been a sell-out. Still, if it is anything like last Tuesday's concert in Seoul, Hong Kong concert-goers should have an evening to remember. After a standing ovation, Dame Kiri sang a haunting Maori song called Po Kare Kare Ano for her final encore, and to her amazement the entire audience joined in - in full harmony. ''Apparently, some of the New Zealand soldiers posted there in the Korean War taught the song to their Korean contacts and it became part of the local musical tradition,'' explained director of IMG Artists and tour organiser, Mark Cowley. ''It was very moving; I don't think there was a dry eye in the house.''