Bangkok — With Thai politics going through one of the most confused and tense periods in years, Prime Minister Prem Tinsulanon-da has left for medical tests in Atlanta. His trip may also be designed to allow the situation in Bangkok to cool off.
At the heart of the present tension seems to be an attempt by at least some senior military officers to reassert their dominant role in Thai politics.
Many observers here feel the supreme commander, Gen. Arthit Kamlang-ek is maneuvering to succeed the prime minister sooner or later - preferably sooner. General Arthit is being supported in his move by an outspoken West Pointer, Gen. Pichitr Kullavanich, who probably hopes eventually to succeed General Arthit.
But despite its tremendous strength, the armed forces faces a number of disadvantages. The public is becoming more open in its opposition to the military domination of politics. The highest echelons of the Army may not be totally united behind General Arthit. And most important, Prem seems still to enjoy the confidence of the royal family.
The introduction of a constitutional monarchy in 1932, some Thai intellectuals say, replaced princes with generals. The majority of prime ministers since then have either had strongmen behind them, or have not lasted long. There have been 14 attempted or successful coups since 1932, as opposed to 15 elections.
Last year, however, the military lost ground. They launched a determined campaign to amend the present Constitution, which does not allow serving officers to hold Cabinet rank. Had the amendment gone through, it would have had the effect of a constitutional coup: The generals would have obtained the power they desired without resorting to extralegal means. The soldiers pushed hard. General Pichitr hinted at military ''exercises'' if the amendment was rejected. But the move was defeated, and the soldiers stayed in their barracks.
This year they seem to be trying a comeback. This summer, a wave of arrests started to raise the political tension. A number of leading members of the Communist Party of Thailand (CPT) - now nearly moribund, but in the 1970s the major threat to the country's security - were arrested. So was a prominent social critic, Sulak Sivaraksa. Most observers suspected that the military was trying demonstrate that the country was still prey to a variety of threats, and thus needed their protective muscle.
The arrests and other incidents were greeted with some skepticism. A respected Thai newspaper theorized that ''influential persons'' were creating confusion as a prelude to a coup. And when last month the police announced the discovery of an alleged communist arms cache in Bangkok, the minister of the interior personally rejected the claim, hinting instead that this too was an effort to keep the situation on the boil.
The military's ambitions surfaced clearly in mid-August, when a group of senior officers petitioned the prime minister to extend Arthit's tenure as supreme commander for two more years after its expiry in October 1985. This would take Arthit to 1987, an election year.
General Arthit's frequent denials of political ambitions are usually attributed to simple modesty. He has in fact been the showing the sort of wide-ranging interest in issues far removed from the Army - including textile policy, the telephone system, and the crime rate - that is normally associated with a prime minister. The extension would keep the general in the public eye until the elections - for, as many generals have discovered, their power base disappears with retirement.
Prem's reponse to the petition was to praise Arthit's skills, express his personal support for the idea, and then consign discussion of the plan to a far-off date.
By this time the prime minister was said to be resting because of chest pains.
In some ways, Prem seemed to have retired to a sort of embattled passivity. Along with regular reports on his health, the Bangkok papers ran slightly incongrous pictures of his security team carrying out their ''routine'' weapons drill in the grounds of the premier's residence.
The appearance of passivity may have been deceptive. After side-stepping the petition, Prem survived a military-inspired effort to debate the constitutional amendment. The day before the debate was due to take place, Arthit suddenly appealed for it to be postponed in the interests of ''unity and solidarity.'' The widespread assumption was that the supreme commander had been unable to marshal the support he needed in Parliament.
This was followed by another apparent blow for Arthit. Early this month, following the annual round of senior military promotions, some 15 newly promoted senior officers called at Prem's residence to express their support for him. According to one report, the generals also expressed their opposition to a coup d'etat.
Around the same time the prime minister received an even more important visitor: Thailand's Queen Sirikit. The royal family has enormous moral influence. A clear demonstration that Prem still enjoys the confidence of the throne would make him virtually unassailable.
Just as he was about to leave for Atlanta, the English-language Bangkok Post, which has in the past served as a conduit for official leaks, announced that ''the powers that be'' wanted Prem to stay in office at least until 1988, to preside over the 60th birthday celebrations of the King. The situation here is still very murky, but if this report proves correct, Prem's future will be assured.