The Reagans have been a swell show and a terrific audience. They demonstrate both again on the "All-Star Gala at Ford's Theatre," an ABC special taped on June 21 and airing at 9 tonight on Channel 7.

In the first row, the Reagans beam, laugh, ooh and ahh over the assembled Vegassy revue held to raise funds for the theater. Nancy Reagan all but gasps when magician David Copperfield balances on the tip of a sword. Later she goes on stage to dance a waltz with Mikhail Baryshnikov while Sammy Cahn sings special lyrics to "Real Live Girl."

Nancy Reagan is a real live wire. The president, in his remarks at the conclusion, says, "I know I'm with the hottest date around." Actor Don Johnson had earlier cited a poll of American men in which a majority said she was the woman they'd most like to spend an evening with.

Sometimes, alas, the Reagans are too good an audience. They do not know when not to laugh. At the gala, they reportedly roared when a comic affected a swish lisp for a joke about San Francisco. Mercifully, this has been cut out of the ABC version. But left in, and hardly more attractive, is the sight of the Reagans convulsed over a cheap Norm Crosby gag about why Jim Bakker probably does not indulge in wife swapping.

The reason, says Norm, is that first you have to have a wife to swap. Ha ha. Did the Reagans really find that tasty, or were they just doing what they thought the cameras expected of them? Crosby's specialty is malaprops, or whatever you call it when someone says "ovulation" instead of "ovation."

Not Funny is one thing you call it.

Others on the eclectic bill are Cab Calloway, Glen Campbell, Maureen McGovern and saxophonist David Sanborn doing a haunting "God Bless the Child." Bea Arthur is awful as the show's emcee, belting out the stars' names with excessive Barnummy bombast, but she has a nice happy spot in the second half, her bawdy tribute to Sophie Tucker.

The telecast tonight is almost certain to get poor ratings, partly because it airs opposite "The Golden Girls," on which Arthur so felicitously stars. While clearly a weird show, the gala is also basically a sound one. The Reagans, with few lapses, play themselves as enthusiastically as the Barrymores might have played the Barrymores.

We are going to miss them -- don't kid yourself! Perhaps they can be entreated to stay around just to fulfil ceremonial functions like this. Nobody stands much chance of doing it better.

'Bay Coven' There's stupid and there's ouch. "Bay Coven" ricochets clunkily from the former to the latter and back again. The NBC movie, Sunday night at 9 on Channel 4, is of the neominimalist school that NBC programming chief Brandon Tartikoff loves trying to pass off as entertainment.

"Bay Coven" is a real page-turner, meaning you should have a stack of magazines on your lap if you plan to suffer through it. Don't watch alone -- have some suitable diversion at the ready. I tried balancing my checkbook but that only took about 20 minutes.

Pamela Sue Martin stars as Linda Lebon, an upwardly mobile Manhattan lawyer whose yupmate is played by Tim Matheson, the poor man's Chevy Chase -- and that's way below the poverty line. Hubby mysteriously insists they move to a creepy 1793 house on Bay Cove's spooky Devlin Island.

That's Devlin as in devil, the party with whom local residents made a soul-selling pact three centuries earlier.

R. Timothy Kring's script is cringe-inducing, but not in the way he probably meant it to be. Director Carl Schenkel sets up some nifty shots with the help of his cinematographer Jack Steyn, but that's about all the imagination expended. One droll touch is the casting of Barbara Billingsley, so long ago Mrs. Cleaver on "Leave It to Beaver," as a key witch, but she doesn't get to do much besides lurk.

The filmmakers are determined to repeat all horror movie cliche's without offering any new variations. In the opening scene a priest sneaks up on a man in church, grabs his shoulder and then, when the man understandably jumps, says, "Sorry, I didn't mean to frighten you." No, he meant to frighten the audience, actually.

A short time later the lawyer gets a jolt when she discovers her husband has been sitting silently in her bedroom for several minutes before making his presence known. "I'm sorry, honey, I didn't mean to startle you," he says. And when two Bay Cove neighbors sneak into the house and scare the wife, one says, "Oh my dear, we didn't mean to rattle your kettle."

This really should have been called "Fake-Out Island."

Since it's a TV movie, it never gets very scary, and Martin wanders around blankly trying to find some furniture to bump into. All too briefly, she has an adorable dog named Rufus. The prettiest girls in the world always seem to have dogs who go by that name.

'Billy Joel' Those who think rock star Billy Joel has already milked the last drop of publicity, and revenue, from his big Soviet tour are dreaming. He's only begun. The megahype continues tonight with the premiere of "Billy Joel From Leningrad, USSR," at 10 on Home Box Office.

If Billy Joel did a concert on the moon, what you'd see mostly is Billy Joel. Also if he did one at the foot of the Grand Tetons. We know this is Leningrad, and that all those gyrating teenskis in the audience are Soviet citizens, but there's precious little sense of locale. It might as well be Passaic.

Most of the local color is contained within the first few minutes, in a wizardly montage of Russian street life skillfully edited by Lisa Hendricks to Prokofiev's "Alexander Nevsky" and, believe it or not, Gershwin's "Rhapsody in Blue." The result is not culture shock -- it's more like bliss. Once Joel appears, the show goes visually slack.

It was in Moscow, not Leningrad, that Joel had a tanty on stage and kicked over his piano, so we don't get to see that. Perhaps he'll do another special and include it there.

Two numbers near the conclusion -- the Beatles' "Back in the USSR," and Joel's own "Big Shot" -- are edited like music videos, and in fact at least one of them has been playing on MTV. But mostly one gets straight concert footage, with too little of the Russians and too much Big Shot.

The show opens with two Joel songs critical of American life: "Allentown," about unemployment in Pennsylvania, and "Goodnight, Saigon," about the plight of U.S. servicemen during the Vietnam war. There are no songs critical of Soviet life.

As a farewell, Joel advises the Russian kids, "Don't take any {expletive} from anybody." The warning seems a tad belated.