Syria doubled its troops and armor ringing Palestine Liberation Organization positions in Lebanon today, deepening the expressions of defeat and dejection among PLO fighters.

PLO Chairman Yasser Arafat, who flew to Tunis yesterday after he was abruptly expelled by Syria, went today to Czechoslovakia for an international peace conference in what was regarded as the first stop in a journey to build support and spare his leaderless forces in Lebanon further reprisals.

In Prague, Arafat made no direct mention of his expulsion from Syria but he condemned "attempts over the past few days by Arabs and non-Arabs to put up violent opposition to the PLO and its independent national decisions," Agence France-Presse reported.

Although a few of the guerrillas in encircled positions in eastern Lebanon's Bekaa Valley talked about fighting the Syrians "from the treetops" and mounting attacks similar to those against Israel, they were words spoken without real conviction.

For most of the downcast fighters interviewed today in Tripoli and the Bekaa Valley, there was the hard recognition that their motley ranks were no match for the beefed-up Syrian armor and commando units, many of whose troops affixed shiny steel bayonets to their rifles today.

"We can't move," said an aide to Khalil Wazir, Arafat's military commander, as he spoke of the humiliation he felt when guerrillas were routinely disarmed as they passed through the reinforced Syrian checkpoints.

"This Syrian Army is very strong fighting Palestinians. But fight Israel?" he asked, clucking his tongue and throwing his head back in the Arab gesture of contempt: "They're afraid."

Wounded pride, anger, fear and a troubling uncertainty about their future--this was the complex mixture of emotions one found among Palestinians loyal to Arafat in a trip today from the northern Lebanese port city of Tripoli, Arafat's isolated and sole remaining stronghold here, to the front lines in the Bekaa Valley in east-central Lebanon near the Syrian border.

Arafat's spokesman, Ahmed Abdel Rahman, said in Tripoli that Arafat had made no decision on whether he would return to Lebanon.

Syrian authorities barred him from Syrian-held territory in Lebanon after deporting him from Damascus yesterday with only six hours' notice, Rahman said. Syria accused Arafat of "lies" and "slander" against Syrian officials in accusing them of aiding PLO forces in the Bekaa mutinying against Arafat's leadership.

The Syrian action caused deep concern among many Arabs. Algerian Foreign Minister Tael Ibrahim met today with Syrian President Hafez Assad. He was the third Arab foreign minister in as many days attempting to mediate the conflict.

The governments of Jordan and Iraq condemned Syria and newspapers in Cairo and the Persian Gulf states were strongly critical.

For Michel Abu Jaudeh, editor of Beirut's daily An Nahar newspaper and a leading columnist in the Arab world, it was an indication of how "the Arab world is torn apart today due to the inability to make war and the failure to make peace."

Rahman said he talked to Arafat last night after his arrival in Tunis and found his morale high. He said Arafat told him, "You know this is not the first time I am in exile."

He had been expelled from Jordan in the "Black September" civil war in 1970 and forced from Beirut last summer after the Israeli siege of the city.

Slowly, painfully, the sad-eyed PLO guerrilla in crumpled olive drab fatigues recalled Arafat's exiles aloud as he and others sat in the dark gloom of an office at the Wavell Palestinian refugee camp near Baalbek in eastern Lebanon.

The older men in the room winced. A couple shyly left. What happens next with the Syrians, the young guerrilla was asked.

"My God, I hope we won't fight each other," he said softly.

Anger was out in the open at the Baddawi refugee camp in Tripoli, separated from the Bekaa by mountains in which Syrian troops are deeply entrenched.

Although Tripoli is in Syrian-held territory, the hostility of many Lebanese and of the Palestinians to the Damascus government is strongest there. On the edge of the city today, there were reinforcements and more Syrian checkpoints and patrols but Syria adhered to its practice of not entering the city itself.

At the Baddawi camp, where Arafat had established part of a provisional headquarters in recent weeks, women, children and armed guerrillas paraded through narrow, dusty streets this morning waving posters of Arafat and chanting slogans condemning Assad and the PLO mutineers.

But in the offices there was a different mood. One of Arafat's bodyguards, allowed to come back to Tripoli yesterday after the PLO leader flew to Tunis, sat grim-faced, head bowed as he spoke bitterly. He cradled a Kalashnikov rifle.

Impulsively he kissed the weapon and said, "We are with this gun and with Arafat."

Washington Post correspondent Jonathan C. Randal reported the following from Baalbek:

Even the followers of Col. Said Musa, also known as Abu Musa, the nominal military leader of the mutinous PLO forces, "were not happy with the expulsion" of Arafat from Syria, according to residents at the Wavell Palestinian refugee camp.

"Many of us differed with Arafat on various major issues," a resident said, "but this decision affects all Palestinians."

Despite the rumors of heightened tensions, a drive through the Bekaa revealed an outwardly relaxed mood. Still, Lebanese sources said casualties since the beginning of the week exceeded 50 killed and wounded and there appeared to be more roadblocks to pass than during a drive two weeks ago.

Lebanese sources insisted that Arafat was correct in asserting that the Syrian Army had helped the rebels, despite the dissidents' claims that they had managed to improve their positions by themselves.

In any event Arafat's supporters were deprived of their main supply route from Syria, and their movements south of Baalbek are governed by the rebels and, to a certain extent, by the Syrians who are the masters of the Bekaa.

But loyalist units are dotted around the area south of Baalbek and are largely intact to the north, according to Lebanese sources.

Six miles southwest of Baalbek, at a rebel headquarters set among fields of hashish, potatoes and wheat, Col. Ziad Sughayer, known as Abu Hazem, said the dissidents now could "completely close" the main roads to the south to the loyalists who "were caught in our pincers."

Although "more troops are joining us every day," he indicated that his movement's numerical strength may still be below that of the loyalists, saying "numbers are less important than the fact that they are in a weak position."

Nonetheless, loyalist troops, including Arafat's deputy Wazir, known as Abu Jihad, were still able to move along roads controlled by Syrian troops.

Told of the despair among Arafat loyalists in Wavell camp, Abu Hazem said: "Arafat misled our people about many things, especially when he said Libya and Syria had intervened to help us. Our movement is motivated by our desire to clean up the PLO, stop the corruption and pursue armed struggle against Israel."

A young Palestinian sentry who left engineering studies at Damascus University to join the rebellion, said, "Our people are half happy and half sad." The unhappy Palestinians, he explained, were those still "brainwashed" by Arafat.