Ronald Reagan has written to Ann Landers for help.

Today, in fact, the president joins Lost in Boston, Confused in St. Louis, Heartbroken in Hoboken and all the other millions of Americans who've turned to Ann Landers for help with problems ranging from transvestism to how to harvest the nuts that fall in a grouchy neighbor's yard.

Of course, The Great Communicator has higher things on his mind (see the column that appears on Page C8 of today's Style section).

"Dear Ann Landers: I am writing about your recent column regarding the letter from 'Terrified in D.C.' I want you to know that I'll take second to none in my concern over the threat of nuclear war." He goes on to outline his disarmament policy for most of the column, an unprecedented forum for policy statements.

On May 17, Landers had advised readers to cut out the column in question and mail it to the White House, which approximately a zillion of them did.

Is this fair? Is this parity with the Russkies? N-O-no, says Reagan, who has a little advice of his own: "Perhaps, instead of sending copies to me, your readers should send copies of your May 17 column to President Brezhnev."

Yes, what he's done is announce what may be the biggest diplomatic event since Secretary of State Alexander Haig started buying those suits with the pin stripes so broad it looks like he's on his way to the St. Valentine's Day Massacre.

The implications are enormous, even heartening. It's like the United Nations opening a mail order branch. No doubt diplomats on both sides of the Iron Curtain are already coming up with plans for the SMALT talks (Strategic Mail Limitation Talks) as guided missiles become guided missives. Political insiders should watch for a merger of the Post Office and the State Deparment, and disarmament advocates must be licking their chops along with their stamps at the greatest opportunity we've had to make sure that nuclear weapons disappear forever: Just take them all to the post office and mail them parcel post.

The whole future of negotiation could be changed. Imagine if all world leaders mailed their problems to Ann Landers instead of heading for the battlefield.

Dear Ann Landers: Lately I've noticed the strangest urge to hold my fingers up in a V-for-victory sign, attack fascist dictators and smoke big cigars. The problem is that I'm a respectable middle-aged woman. Please, Ann, don't tell me to see a minister; I've got a whole cabinet full of them and they're just as crazy as I am.--Frowning on Downing Street

Dear Frowning: I asked a top political analyst about your problem, and he tells me you're suffering from the dread "Churchill Syndrome." Have you considered an island vacation in the South Atlantic?

Dear Ann Landers: Can't people get it through their heads that South American generals don't pin all those medals on their uniforms for glory? Ann, it's only part of my job as a head of state to appear on television looking like I just walked through an Army-Navy store with a magnet. Another thing: I'm sick of people calling me a chairborne ranger. It's not true that I've never fought in a war; we've been fighting one against the Argentine people for years.--Pampered in the Pampas

Dear Pampered: Have you considered an island vacation in the South Atlantic?

Dear Ann Landers: I blew up the King David hotel. Then I refused to give the West Bank to the Palestinians. Then I bombed a nuclear reactor in Iraq. Then I invaded Lebanon. Please print this as a warning to others.--Taking a Stand in the Holy Land

Dear Stand: When we begin the beguine, who knows where it will end?

Dear Ann Landers: You'd think that I could run my own liberation organization without people making nasty remarks about my 5 o'clock shadow. You'd think I could wear my pistol to the United Nations and still have everyone take me seriously as a peacemaker. You'd think that the world would understand that terrorists have rights too.--Overdrawn at the West Bank

Dear Overdrawn: That's what you'd think, wouldn't you? That's just what you'd think.

Dear Ann Landers: Okay. You have jeans, we like jeans. You have jazz, we like jazz. So why is nobody laughing at our Polish jokes?--Wowing 'Em in Moscow

Dear Wow: Try Afghani jokes, not to mention Angolese, Yemenese, Somalian, Cuban, Czechoslovakian . . .

Confidential to the Gipper: Instead of making extemporaneous mistakes that convince Europeans they're about to be bombed into the Stone Age, take a hint from me. Play it safe and just recycle material from decades ago. You didn't get caught at it in 1980, did you?