Thailand's Parliament has blocked an Army-backed move to reopen discussion of permitting military officers to join the Cabinet thus averting a confrontation between Prime Minister Prem Tinsulanond and the armed forces.

The Parliament voted 371 to 76 Monday to postpone consideration of the motion following a request by the supreme commander, Gen. Arthit Kamlang-ek, Sunday that the issue be put off for the sake of national unity.

"Prem has won a battle," said a western diplomat. "The fact the military backed off can count as a victory for him." However, the issue and its inherent tensions are considered almost certain to crop up again, probably in a parliamentary session next April, diplomats and Thai observers said.

The postponement of the Army move followed two months of military and political developments that had alarmed some segments of Thai society and provoked protests from students and human rights groups. The Army was seeking a reversal of a parliamentary vote last year precluding officers in the Cabinet.

The developments included: rounding up in July of 22 suspected Communists in Bangkok; arrest in August of prominent writer and social critic Sulak Sivaraksa and two associates; a move last month to extend the military tenure of Gen. Arthit beyond his mandatory retirement at age 60 next year; introduction of the parliamentary motion, and the announcement Monday of an annual military reshuffle that consolidated Arthit's hold on the Army.

Western diplomats question whether these events are related, but some Thai observers see them as part of a conservative trend involving the continued rise of Arthit and restoration of the military's dominant political role following efforts by civilian parties to promote parliamentary democracy.

The United States has made known its support for a moderate parliamentary government and political pluralism in Thailand, a U.S. ally on the Southeast Asian mainland. But the United States also has a close relationship with the Thai military dating from the Vietnam War and is the major supplier for the Thai armed forces.

Arthit's continued rise was confirmed in Monday's military reshuffle affecting 352 officers. A strong backer, Maj. Gen. Pichit Kullavanich, was promoted to commander of the most important of four regional commands, the one that includes the capital, Bangkok.

The outspoken Pichit, 52, a West Point graduate who served with Thai forces in Vietnam, has promoted a bid to extend Arthit's tenure as supreme commander and Army commander-in-chief for two years.

Pichit, who is widely seen as having ambitions of his own to become prime minister, also has strongly supported efforts to amend the constitution to allow civil servants, including military officers, to hold political posts in the government such as Cabinet positions.

Faced with intense military lobbying last month for Arthit's extension, Prime Minister Prem praised Arthit and agreed that extending his service was a "good proposal." But he deferred the matter by saying he would "consider action in accordance with the legal process."

Tension between the government and military peaked with the introduction in Parliament of the Army-backed motion to reinterpret last year's vote on the constitutional amendment bill, which was defeated when the speaker of Parliament ruled on a technicality that it had failed to get the necessary majority. The motion was seen as a move to pave the way for Arthit to assume a Cabinet post and get into position to succeed Prem.

Prem, under pressure, then retired to his residence on grounds of illness and said through a spokesman that he would go to the United States Sept. 14 for a complete medical checkup and an extended rest.

Speculation grew that Prem, 64, the longest serving prime minister of a civilian administration in recent Thai history and himself a retired Army general, was being pushed out by the military or that efforts were underway to mount Thailand's 15th coup attempt since 1932. However, this speculation was quelled, and Prem's position received a major boost, when Queen Sirikit, the consort of revered King Bhumibol Adulyadej, called on the prime minister Friday. Newspapers published a palace-distributed photograph of them at his home.

Arthit also emerged with enhanced stature by issuing his postponement call and thereby "calming the waves" of a government crisis, the diplomat said. "Regardless of whether he caused them all in the first place, Arthit got credit for calming them."

The importance and sensitivity attached to the royal family, which in principle remains aloof from politics, was illustrated by the arrest Aug. 5 of writer Sulak on charges of attacking the sovereign for comments in his book "Unmasking Thai Society."

The arrest in Bangkok by the police Special Branch aroused expressions of international concern from academics and human rights activists in Asia and the United States.

In response, Interior Minister Sitthi Jirarote warned foreigners not to interfere with Thai legal processes.

Sulak has been released on $22,000 bail and is due to go on trial shortly.

It has not been clear whether the military had anything to do with Sulak's arrest, but some western diplomats were inclined to think the case was separate from the other political and military developments involved in the latest government-military face-off.

Likewise, it was unclear whether the earlier arrest of the 22 suspected Communists in Bangkok represented a military move against Prem's policy of using chiefly political means and amnesties to combat the Communist Party of Thailand's increasingly feeble insurgency. Some political analysts say it is more likely that the Communist suspects were arrested because, as police charge, they exceeded the bounds of permissibility by opening contacts with Communist authorities in Vietnam and Laos.

Others have speculated that with the arrests, the military was trying to provoke student demonstrations and unrest that would have provided a rationale for a coup. In any case, no such upheaval materialized, and the prospect of a coup now is generally ruled out.

"The essential point is that the people who are pushing to unseat Prem are trying to do it through legal means," said a western diplomat. "It's much harder to have a coup now than it used to be."