Yasser Arafat, now almost the only Palestinian leader left in Beirut, is providing the last bit of drama in Lebanon's three months of agony since the Israeli invasion.

As the Israeli-forced withdrawal of the Palestine Liberation Organization from Beirut entered its final stages with the departure of about 1,700 more guerrillas by land and sea today, the only remaining questions are when and how the PLO chairman will leave and where he will go.

Most of the best-known leaders of the myriad of organizations grouped under the PLO umbrella departed yesterday by sea and are now in Syria, including George Habash, leader of the Popular Front for the Liberation of Palestine; Nayef Hawatmeh, from the Democratic Front for the Liberation of Palestine, and Ahmed Jibril, of the PFLP-General Command. Today, Arafat's top military aide, Abu Jihad, sailed to Syria.

The overland departure for Damascus of 1,200 Palestinians today was more subdued than the earlier raucous evacuations marked by ear-splitting gunfire. The only epic moment left is Arafat's farewell, if he feels he is secure enough to go in public as he has said he will do.

A Greek government spokesman told reporters Sunday that Arafat plans a visit there during the week. His trip will "coincide with the official visit of President Francois Mitterrand" of France on Wednesday and Thursday, the spokesman added. There was no official confirmation of the report in Beirut.

Beirut, once the tourist mecca of the Middle East, now reduced to a war-battered shambles, seemed nonchalant about the impending departure of the best-known political figure in the country.

It was as if Beirut's residents, after 77 days of warfare, finally believed they could relax slightly.

After all, it was Sunday and even though there has been plenty of beach time since West Beirut's commercial life has been closed down for almost three months, Sunday is a special day to go to the beach, said Etidal Abul Hassan, 18, a secretary.

So the Sporting Club beach, one of the few to escape Israeli shelling, was crowded, and nobody seemed to notice -- or care -- that half a mile away in a once-posh district Syrian tanks and antiaircraft guns were being loaded on transporters to prepare for the beginning of the Syrian Army exodus Monday.

Just above the beach a Syrian soldier made it clear that even though he was departing he had not fought for the last time in Lebanon.

"Instead of fighting here we will fight Israel somewhere else, perhaps in the Bekaa Valley" in eastern Lebanon, he said.

Wearing a T-shirt advertising a cream for "perfect skin care," he was standing in one of Beirut's contributions to modernistic architecture. The shell-pocked, seven-story building has huge round windows, like giant portholes. All 42 are broken.

But not all of Beirut's suffering and damage have been caused by the Israeli invasion. At the Green Line, the no man's land separating Christian East Beirut from the Moslem western part of the city, weeds are overgrown on the earthen barricades thrown up when the factions began the nation's civil war seven years ago.

The Green Line was formerly Beirut's downtown area. Practically every building is damaged, and few people not involved in the fighting have ventured into the area since the war started in 1975. Today people were gingerly returning, although they said gunshots echoing through the streets were fired by a sniper.

Wafic Mikata brought his two young sons down to the area to see the luggage store he abandoned in 1975. He hopes to reopen next month but could not get into the store today because he had lost the keys after so long.

A Moslem, he was hopeful that Christian President-elect Bashir Gemayel could bring peace to the country.

"We need each other. We are forced to come together," he said.

Many Moslems think otherwise, however, fearful of the bloody record of Gemayel's militia, which is loyal to his Phalangist Party.

At the beach, hardly a head turned as a man and four girls fired round after round from an AK47 rifle into the sea. Members of a Moslem leftist group, the girls, age 12 to 17, were being taught to fire.

Sausan Haj, 12, blinked as she fired. Even though the man held the rifle barrel it jumped in the arms of the slight girl.

"The Palestinians are finished here," she said, "so we must learn to fight."

Whom was she going to fight, she was asked.

Not hesitating for a minute, she said, "The Israelis and the Phalange."