Matthew Broderick is one of the hottest young stars here today. Under the direction of Gene Saks he opens Thursday in "Biloxi Blues," Neil Simon's sequel to "Brighton Beach Memoirs" (Neil Simon, 250 W. 52nd St.).

Three just for laughs: "Crossing the Bar," a comedy by Michael Zettler, which opened last Thursday at the Playhouse 91 (316 E. 91st St.); "Digby," a comedy by Joseph Dougherty, with the brilliant team of Anthony Heald and Roxanne Hart (Manhattan Theater Club at City Center, 131 W. 55th St.); and "The Foreigner," a very funny play by Larry Shue, with Kevin Geer as a lovable half-wit (Astor Place Theater, 434 Lafayette St.).

"The Hitch-Hikers" has the home-spun humor found in the lively South of Eudora Welty's imagination. It is adapted from one of the author's short stories (WPA, 138 Fifth Ave.).

Two for the heart: "Joe Egg," the production of Peter Nichols' play about the trials of the parents of an incurable brain-damaged spastic, starring Jim Dale and Stockard Channing, opens tomorrow on Broadway (Longacre, 220 W. 48th St.). And "As Is," a play about AIDS that has received amazing critical acclaim from all quarters (Circle Rep, 99 Seventh Ave. South).