The interior of a Washington taxi can be a den of the bizarre.

If the driver doesn't have 137 religious medallions stuck magnetically to his dashboard, he has 13,000 unused matchbooks secured to the sun visor with a single rubber band.

If the driver isn't beefing to you about his other job at the Commerce Department, he is beefing at you to put out that cigarette. If the cab isn't dirty, it's freezing . If it isn't stuffy, some guy has left a newspaper all over the place.

It's enough to give Metrobuses a good name.

But Donald Kesecker and his Diamond Cab Number 52 are a world apart. Some would say a world apart from its senses. Kesecker would say a world apart from the grumpiness and gruffness of the typical taxi experience. Whatever, the smiles on the faces of his passengers are real.

It is not the Chopin on Kesecker's radio. It is not just the D.C. phone books and the box of Kleenex in the rear window well. The chief reason is Kesecker's language wheel.

Underneath the center of the dashboard, Kesecker has mounted a roll of white paper towels. Around the towels, he has fastened a sheet of yellow paper. On the sheet of paper are fourteen common phrases in 33 languages.

You want Kesecker to say goodbye to you in Amharic? Easy. You want him to let you know in Swedish when you've reached your destination? Nothing to it. You're dying to be asked in Japanese how you are?

All it takes is a moment while Kesecker's fingers do some walking.

"I play Embassy Row a lot, and every other passenger is a foreigner," Kesecker explained. "This delights the foreigner. But it also delights me. It helps business, and it helps me learn languages."

All 403 entries on Kesecker's wheel of fortunes are spelled out phonetically, for easy reading. Many relate directly to a taxi ride ("Are you late?", "Where are you going?", "Here we are"). Almost all are more useful to Kesecker than to his passenger.

Kesecker constantly updates his wheel - either refining pronunciations of phrases on the recommendations of passengers or adding new languages.

He began with Japanese, "and I never thought I'd get beyond that, to tell you the truth." But he has since ventured far, far afield.

For example, about a year ago, after many of his passengers suggested it, Kesecker added the 33rd language to his wheel: Southern.

"Southern's" 14 entries would probably enrage most Dixie folk, because they are dripping with cliche ("Whar y'all gawn?," "Ah don't speak . . ."). But Kesecker know who's president. In fact, it was a Carterite Georgian who first gave Kesecker the idea.

He also knows which side of his bread bears the butter. "Oh yes, sure it helps with tips," Kesecker acknowledged. He said he can't estimate how much, "but I know it's sizable."

Kesecker, 55, has been driving a cab here for 25 years. But it was not until three years ago that he went word-happy.

"I was watching some of those crazy stunts on "Candid Camera," and I said, "Hey, I could have some fun, too.'"

With the help of a Japanese neighbor, he puzzled out The Fourteen Phrases in Japanese. Over the months and years, the phrases in other tongues came from reference books - and passengers. The two most popular stops on the wheel are Arabic and Spanish, but Kesecker said every language crops up at least once a year.

What also crops up is the sort of fun Kesecker originally had in mind.

He delights in having a foreigner get in the cab and ask, in halting English, to be taken to the State Department. If the man is, say, French, Kesecker will wheel his wheel, turn in his seat and ask the man in French if he speaks English.

"The responses are really something," Kesecker said. "They just sit there frozen for a few seconds, as if they can't believe this is happening." But matters warm up from there. "One Japanese guy, I asked him a question in Japanese, and he was laughing all the way to the Federal Trade Commission."

Kesecker never pushes too far, though. For one thing, his 14 phrases are so abbreviated that a full conversation would be impossible. For another, foreigners think you're making fun of them," Kesecker said.

But far more offer Kesecker their friendship. His language wheel has gotten him invitations to several countries. One Japanese passenger offered to serve as Kesecker's guide for an entire month's visit in Tokyo. Kesecker has not accepted any invitations, "but I certainly have them in mind."

He also has in mind the impression he leaves on passengers. "I'm just a taxi driver, but I feel that, when they go back to their country, they will remember one American who was kind and friendly."

Just as language is dynamic, so is Kesecker's language wheel. The 33 most common languages and phrases may already be at his fingertips, but there are always more.

This month he is working on Bulgarian and Czechoslovakian. And he is planning to add phrases 15, 16 and 17 to all his language soon. They will enable him to say "How much?," "Sorry" and "Happy to do it."

"It keeps you alert," says Donald Kesecker, as he swings his Mercury out into rush hour traffic. "It helps me financially and mentally, and it delights the passengers. It has every advantage."