THE Asian cinema's karate king Jackie Chan came on board the starship Planet Hollywood yesterday in a hands-on sort of way. Breaking off his hectic filming schedule, Chan donated his handprints to the restaurant, thus joining Sylvester Stallone and Steven Seagal in this concrete gesture. While he was in a generous mood, Chan also gave the restaurant the traditional Chinese wine jar that he uses in his latest movie Drunken Master II. With Chan yesterday was local movie mogul Raymond Chow and together they cut the ribbon to officially open the Planet Hollywood merchandise shop, which is becoming quite a tourist attraction along Canton Road, Tsim Sha Tsui. One of the nicest guys in show business, Chan told Keeping Posted that he was looking forward to the opening of Planet Hollywood ''not so much for the food but for the fun''. He won't have long to wait. Planet Hollywood Hong Kong will open on May 29 - and that's official. It will be launched with a bash that is beginning to look like, with apologies to Saddam Hussein, the mother of all parties. Apart from partners Stallone, Jean-Claude Van Damme, Bruce Willis and Arnold Schwarzenegger (who will probably come a day or two earlier to instruct the chefs on how to prepare his mom's apple strudel, which is one of the featured dishes), confirmed to attend so far are Whoopi Goldberg, Danny Glover and Cindy Crawford. But back to Chan. How about the East-meets-West cinematic collaboration between Sly and him? ''That's still definitely on,'' Chan said, ''but I'm leaving it to Stallone to come up with a suitable script. He knows what makes good box office material in the international market better than I do. ''Maybe we'll be able to work on it a bit more when he comes to Hong Kong for the Planet Hollywood opening.''