AFTER almost a year away, the Queen Bee of this town's social royalty, Cristal Li, is set to return at the weekend to reclaim her throne. How do we know she has not abdicated and is really coming back this time around? Because we understand six (designer, naturally) suitcases of Cristal's possessions preceded her to Hong Kong. For the past few months, Cristal - wife of Kowloon Dairy tycoon and Jockey Club steward Alan Li - has been travelling the globe, from Europe to Africa and Argentina, and all points in between, working on her tan. Now sated and sauteed, she returns in time to prepare for a happy event that awaits the Li clan, the marriage of third son, Didier, to Michelle Huthart in November. We hear Cristal's close pal, fellow Frenchwoman Chantal Slim is planning a surprise ''feast'' to celebrate her return.