Beirut — More troubles in the two Yemeni republics perched against Saudi Arabia's southwest corner bode ill for that super-conservative kingdom. In recent weeks, the following snippets of news have emerged from the 5 -million-strong North Yemen and the pro-Soviet 1.7-million-strong People's Democratic Republicof (South) Yemen (PDRY):
* In the noth, former Foreign Minister Abdallah al-Asnag has been arrested, accused of planting listening devices in President Ali Abdullah Saleh's office.
* North Yemeni intelligence chief Muhammad Khamis was reported killed at the end of January. Mr. Khamis, like Mr. Asnag, was considered pro-Saudi and pro-Western.
* In the south, travelers from the PDRY capital, Aden, said during February that Politburo member and former Foreign Minister Saleh Muti had been executed, along with his supporters.
Saudi Arabia has every reason to be concerned about developments in the two Yemens, which together contribute a million members of the Saudi kingdom's large expatriate to the Saudi kingdom's large expatriate work force. The Saudis, too, are intensely worried by the presence of East-bloc advisers in South Yemen (recently reported to total around 1,500), and by Soviet activities in Aden's splendid British-built port.
With South Yemen firmly in the Soviet orbit over the past decade. Saudi Arabia's relations have traditionally been far stronger with the north. When a border war erupted between the Yemens in February 1979, the Saudis mobilized their Army in support of the north, and footed the bill for subsequent shipments of American arms there.
But since then, the northern president has distanced himself progressively from Saudi influence. The latest moves against Saudi Arabia's allies in the republic can be seen as an intensification of this trend.
The fertile mountains of North Yemen were dubbed by Roman travelers Arabia Felix (Happy Arabia). But in recent times they have seen more than their share of political turmoil. A long, ugly civil war in the 1960s pitted pro-Saudi monarchists against Egyptian-backed Army officers.
The eventual compromise between those sides drew the dimensions of the present unstable equilibrium there: Power is untidily shared in the north's capital, Sanaa, between the Army and representatives of the tribes. Although the tribes remain strong, each in its particular home base, the Army is the only organization with any potential for republic-wide loyalty. But with politics firmly entrenched in the barracks, successive purges have weakened and split the officer corps.
Neither of the Yemens has been able to find oil in commercial quantities. But the remittances from emigrant workers brought the promise of prosperity, especially to North Yemen, whose landscape remains largely that of the traditional, spectacular mud-brick skyscrapers, even in the capital.
Most of those hopes proved illusory, though, chewed away in hours-long sessions with the national narcotic, qat, which absorbs an incredible proportion of national income.
North Yemen has thus been a fertile arena for a three-way struggle among the conservatives of Saudi Arabia, the brother-Yemenis of the south, and the distant Baathist ideologues of Iraq. Iraq has been pouring money into the Yemens over the past years, and is reaping the reward with bought-and-paid-for supplies of Soviet weapons from Yemeni arsenals.
The Saudis have retained influence with many tribes, though this is reported waning, and a longstanding border dispute with the Saudis continues to sour Saudi-Yemeni relations. The pan-Yemeni instinct toward union with the south remains strong, but northerners are still wary of the rigid socialism in the south.
The two republics, which are both formally committed to eventual unity, continue to have an effect on each other's policies. This was strikingly evidenced in June 1978, when President Saleh's predecessor in the north was blown up by a briefcase bomb. Thirty hours later, his southern colleague, Salem Ali Robaya, was also overthrown. Among the charges against him was organizing the dispatch of that bomb.
Most recently, it is significant that former Foreign Minister Asnag, accused by the north of spying for the Saudis, is himself an exiled South Yemeni, deeply opposed to the regime in Aden.
In Aden, meanwhile, the execution of Politburo member Muti is a furter step in the purging of the historic South Yemeni leadership that started with Rubiea Ali's overthrow. This was the leadership that spearheaded the embryo republic's independence fight against the British in the 1960s, then steered it into the socialist camp after winning a post-indenpendence power struggle in 1969.
But the purge of that leadership does not mean that Soviet influence in the south is on th e wane.