He looks the part so well. Swarthy Complexion tanned year 'round black hair touched with gray calls at the temples. Marboros in an amber cigrette holder. Elizabeth Taylor calls him "Rudi" (for Rudolph Valentino).

He arrives, this King of Chic, as Italian designer Valentino seems always to have been called, in a camelcolored pinwale corduroy suit, blue striped shirt and wool tie, on an early night from New York. He is carrying his own luggage like Jimmy Carter And chewing gum which he says helps him relax and even sleep on the plane.

IS this the new casual chic being touted in New York as the coming an attitude more classic than 1960s more relaxed than the 1950s? For Valentino, the only bow to the looser style is the intentional open button on his barrel cuff shirt sleeve. "But easier clothes are coming for men," says the designer in a perfectly fitted outfit.

He is the first of a dozen or so designers who will be coming to Washington over the next two weeks to introduce their lines. And he does it with elaborate trappings: a limousine at the airport, the presidential suite at the Watergate Hotel, orchids in the room, television and press interviews, lunch at Sans Souci, a tour of the Matisse collection with a personal greeting from the National Gallery's director. Carter Brown. cocktails under a tent at the Watergate. plus a party in his honor at Pisces. And back to New York the same day.

Why does he rate? For starters, there are the clients, who read like a listing of international blue bloods.

"The Empress Farah Dibah loved the blousons," he mentions in passing, and "Jackie Onassis stopped by on Friday, bought the poncho and matching skirt." Other customers include Marella Agneli (of the Flat fmily), Audrey Hepburn, Marie Helence and Olympia de Rothschild.

And there are the houses, one in Rome on the Appian Way, a show piece in Capri with a room bulit around his blue and white porcelains, and a new house in Gstad. "Houses," he says, "are my luxe."

While the houses decorated to the nth degree are an important showcase - a new apartment in New York has just been decorated by Fracoise de la Renta - he's very much the center of a party scene. In New York last week it was parties every night in his honor, or he was out dancing at Studio 54, the disco.

He used to give the most lavish parties himself. Once he did an extravaganza at the Hotel Pierre under a specially built tent with an Arabian Nights theme. Another he gave at Jackie O, a night club in Rome, for this own birthday, but all the jestsetters in black and white, and "a (starlet) coming out of a cake," he recalls.

Those parties are finished now. "They are too expensive ," he says. "You cannot spend a fortune when the times are so serious."

And of course the final and conclusive reasons why he rates are the clothes. The collection now at his boutique of the Watergate is, he says, inspired by the mad king Lud. wig of Bavaria as portrayed in the Lucchino Visconti movie. "I like the personnage," says Valentino, who clearly likes the lifestyle of the rich and so designs ponchos and skirts for the races, with velvet suits with ruffled collars, big shawls, spats and felt hats to go with them.

("You know it was criticized a lot for looking too rich," admits Valentino. But he adds quickly "It is selling very well in Europe and New York.")

Priices range between $500 and $600 for a poncho, $200 to $300 for a skirt, $125 to $250 for blouses and $150 to $200 for shawls. "You don't have to wear all of the parts of each costume, " Valentino explains. "You could buy just the prices you wanted and they would be much less expensive."

He insists on luxury for his fabrics and workmanship. "I cannot touch one fabric if it is not beautiful cashmere or silk," he sayds. "If it has one percentage of synthetic, I know it, even without seeing the label."

If the fun and games have slowed a little, it's not only the "serious times" but the fact that Valentino is now big business.

His partner keeps track on the figures and he says he doesn't know them for sure, but a recent trade report pegged his wholesale volume at more than $35 million with 100 boutiques for his women's clothes (the newest being the one that opens today at Les Champs in the Watergate), 25 men's boutique and a growing home furnshings business.

With all that has he had to change his definition of chic?

"It's more causal, do not perfect, not so chi ch," he says.

What's not chic (or "ex-chic" as he calls it) is being perfectly dressed from head to toe, and yet "when you move it is a disaster, so ungraceful." Later he adds, "its ridculous to be so perfect."

"Chic," he concludes, "is simplicity," dismissing flamboyant garb like peasant dresses and extravagant ballgowns. "They don't fit into small chairs. They are no longer suitable."

With that, the King of Chic gets into his limousine with his entourage and drives off to his next appointment.