You talk about avant garde! At the disco-restaurant Les Bains Douches they are reviving the '70s.

Once, where the restaurant is now, there were tiled-floor showers and dress rooms. The dance floor was the steam bath. The disc jockey's area was the sauna. The cooling off pool it still there but now contains a checkerboard on the bottom where a diver moves huge checkers to the calls of playng customers.

This is Les Bains Douches, a former public bath and now Paris' hot new disco-cum-restaurant which designer Karl Lagerfeld calls "the only place to go." He pronounces last year's "in" disco, Le Palace, as "demode." (Lagerfeld, whose home and heart are entrenched in the 18th century, is always first with his feet in front-running discos.)

"There is a good mix of people, good music and the restaurant isn't bad either," Lagerfeld says of Les Bains Douches.

The mix ranges from Lagerfeld and his friend, Count Jacques de Bascher, to the punks with their slick black or colored hair, and the nouvelle vague crowd dressed a la 1950s and 1960s with peg pants and white socks, strapless prom dresses and ballet slippers and even Bermuda shorts.

Fashion trendies Lou Lou LaFalaise Klossowski and Paloma Picasso go there occasionally. So do Kenzo and other designers. Guy Bourdin has photographed the next album cover for Boz Scaggs there.

Antique dealers Jacques Renault, 30, and Fabrice Coat, 25, started Les Bains Douches. They found it by accident. They'd gone to what was called Les Bains Guerbois, a public bath that had not been used for at least four years, to track down some statues and furniture they thought they might possibly buy for resale.

All that was forgotten when they saw the bath house and decided that the imposing appearance of the building, with huge statuary outside and a grand entrance staircase, made it a natural for a restaurant, and disco. Its location on a small street near the Beaubourg Museum and Les Halles was a decided plus.

Renault insists he had never before been inside a disco but decided to open Les Bains Douches "only because it is fun to do something different."

Coat did not frequent discos either. "I would go with friends to play pin ball at the Bus Palladium when I was young," he says.

On a recent night the two were working the cash register, taking dinner orders, checking guests at the door, inspecting the dance floor and stopping for a glass of Perrier with their wives in the Chinese bar. They do the ordering and the accounting as well.

They started the place modestly. The chef is straight out of school. The changes in decor, done by a decorator friend, were minimal: a splash of neon over a lacquer red barroom, the removal of most of the plumbing fixtures from the baths.

"We didn't spend much money." says Renault. "We didn't have it. Neither do your friends who are in this with us. And I am not looking to be paid much. I don't have much experience to be paid for."

"It's fun to start a business," adds Coat, "especially when it works well."

The music is "Hot Funky" by Hot Chocolate and on the crowded dance floor couples do jerky, robot motions to the loud, synthetic sounds. One girl wears a yellow, strapless prom dress with white ballet slippers, her hair like June Allyson's plastic flowers around her wrist. Another has a Coureges mini with short, white Courreges boots. The guys look like Marlon Brando clones: slick black hair, white T-shirts, whites socks and loafers.

Occasionally someone shows up in a headband and hippie beads. "Those kids have started to revive the 1970s," says the disc jockey.

On a platform, against a backdrop of white Venetian blinds, dancers wear headsets wired into the sound system. "They were slow to start using them," explains model Violetta Sanchez. "They thought the headsets would inhibit the dancing." Actually, they have quite the opposite effect.

At one corner of the room, some young dancers stare through a peephole at movies. Usually there are clips from westerns or other old flicks.Never porn.

Twice monthly there are small concerts downstairs, mostly English or Jamaican reggae. The group Sucidide and others, The Cramps, Rachelk Sweet and The Shirt, were there recently. An English new wave group, Joy Divison, is due next month. Concert tickets are 40 francs ( $10).

There is no charge to come to the disco, but all drinks are 50 francs ($12.50) and the room is so hot, in spite of the recently added air conditioners, almost everyone needs at least one drink.

Renault and Coat say there are no drugs, that they are ever alert. And the "ciggie girl" and "toilette girl" are watching full time, too, they add.

Renault and Coat still dabble in antiques and say they don't know how long the club will be a success, or how long they will stick with it.

"We'll stay as long as it is fun," says Coat, checking the crowd outside the place at 2 in the morning. "When it stops being fun, we'll move on to something else."