The avoidance of collision with President Carter over Israels latest affront on new West Bank settlements may encourage Prime Minister Menachem Begin to escalate his game of "chicken" with a daring raid into southern Lebanon.

Diplomatic experts give odds of just under 50-50 for a swift Israeli move across the border against Palestine Liberation Organization (PLO: guerrilas, under the attractive guise of protecting Lebanese Cheristians. The raid probably would last no longer than 24 or 43 hours and would have to come soon - before the planned evacuation of PLO guerrillas from their southern Lebanon bases.

The purpose of such a raid: undermining the U.S. effort to persuade the PLO to accept Israel as a permanent state under terms of United Nations Resolutaion 242. If Begin sabotage U.S. policy so frontally, Jimmy Carter would face his toughest choice between swerving or accepting the political consequence of a painful head-on collision with Israel.

An Israeli assault across the border against PLO concentrations, intended to destroy as many guerrillas and installations as possible, also would serve some less obvious purposes for Begin. It would heighten PLO hatred of Israel and weaken the PLO's moderates, including Yasser Arafat, who are believed ready to go along with the U.S. plan.

An incursion of the type successfully employed on earlier occasions against the PLO in both Lebanon and Jordan would follow three successive Israeli affronts to the Carter peace plan:

First Begin's "legalization" of three Jewish settlements on the Palestinian West Bank, second, a major tightening of Israel's occupation policies over one million Arabs in the West Bank and Gara, now under Israel military control; third, the government's approval last week of three new Jewish settlements.

Besides hardening PLO resistance to Israel as a state, each of those steps was calculated to send, Carter this warning: Do not keep trying to bringto send Carter this warning: Do not keep trying to bring the PLO into center of peace efforts.

Diplomats here with access to Israeli thinking say nothing has so infuriated. Begin as the "unfriendly" moves of Carter in trying to give international credibility and respectability to the PLO. Thus, each time the United States steps up its efforts to convert the PLO from outsider to insider - as a trusted party to Mideast negotiations - Begin counters with a new more against the Carter peace plan.

This game of chicken appears to be working to Israel's advantage. Every time he swerves to avoid the collision, Carter looks weak and vacillating. On July 28, the President said he had told Begin "very strongly" of his "deep concern" that no new settlements be established. Yet, the administration's response to the three new settlements was couched in flabby diplomatic language and was delivered not by the White House but by State Department spokesman Hodding Carter Jr.

Given the lack of U.S. countermeasures against Begin's bold rebuffs of Carter. Begin might well be tempted to cross the Lebanese border. The poorly organized PLO irregulars, numbering between 3,000 and 5,000 and scattered over the 20 miles or so between the border the Litani River, would have no chance against overwhelming Israeli military force.

The presence of the PLO force as a magnet for Israeli intervention frightens both Lebanon and Syria. Those two countries, along with Egypt and Saudi Arabia, are seeking to tranfer the PLO gurrillas northward, far out of southern Lebanon - thereby removing the magnet.

Despite repeated PLO pledges and months of works, the PLO irregulars have not yet been separated from the Christian villages that dominate southern Lebanon. One reason: Aided by Israeli artillery and supplied with Israeli rifles and supplied with Israeli been more willing to break off the war than the PLO.

Nevertheless, the PLO force will finally be removed, perhaps within two months, making Isareli intervention across the border more difficult to justify politically. But today, conditions are ideal for Israel; a sudden sweep into PLO areas to protect the Christians, a quick return to Israel, a dramatic display to the world press of grateful Lebanese villagers giving flowers to Israeli soldiers.

Impossible? Far from it, in the opinion of this government's closest students of Begin and his bold, activist, masterful policies. To Menachem Begin, a genuine U.S.-PLO rapprochement holds deadly peril for Israel. The major question today is how far he will go in risking collision with Washington to guard against that peril.