S. African right moves into open

One of the most unsettled periods in the history of South Africa's ruling Afrikaners appears to have come to an end. This probably brings both relief and a new kind of worry to the government of Prime Minister Pieter W. Botha.

The relief is that a ''fifth column'' of right-wing opposition has been brought out into the open. The worry is that right-wing forces may coalesce and present a more serious threat to the government.

This is how political analysts here assess the resignation this week of Dr. Andries Treurnicht from the Afrikaner Broederbond, the once-secret political organization that for 36 years has united Afrikaners behind National Party rule. Treurnicht bolted from the National Party two years ago unhappy with Botha's so-called ''reformist'' policies and founded the right-wing Conservative Party.

Last month, Treurnicht and other right-wing leaders formed the Afrikaner Volkswag (People's Guard), a conservative alternative to the Broederbond. The Volkswag's broad support among right-wingers might provide the cohesiveness South Africa's far right has so far lacked.

Analysts here are divided on whether a distinct right-wing movement will restrain or embolden Botha on his moderate course of so-called ''reform.''

''The government will welcome'' Treurnicht's resignation, predicted William Esterhuyse, a political scientist at the University of Stellenbosch.

Esterhuyse thinks Treurnicht's departure means the National Party's political split two years ago has now washed through all the key Afrikaner cultural and political institutions. The result will be firmer footing for Botha in loyalist organizations, like the Broederbond, where there had been ''uneasy'' support.

''I believe the government will need to look over its shoulder to the right less now,'' Esterhuyse said.

Other analysts believe Botha will exhibit caution as he contemplates the impact of a slowly coalescing right-wing threat. Right-wing forces are on the move, although many believe the political base of this movement is fairly narrow.

National Party watcher Willem Kleynhans of the University of South Africa believes the far right poses a formidable threat to the government that may be exercised through the Volkswag.

One reason for the right wing's strength is that its leaders are past members of the Afrikaner establishment. Treurnicht was once chairman of the Broederbond, leader of the National Party in the powerful Transvaal Province, and member of Botha's Cabinet.

The chairman of the Volkswag is Carel Boshoff, a past chairman of the Broederbond and son-in-law of Dr. Hendrik Verwoerd, who was considered the architect of apartheid.

Like Treurnicht, Boshoff refused to accept Botha's plan for ending exclusive white rule in South Africa. Botha has paved the way for Coloreds (persons of mixed race descent) and Indians to join whites as junior partners in Parliament. The new Parliament is scheduled to open in September. South Africa's far right has already demonstrated some political potency. The Conservative Party has won two seats in Parliament in the past two years. But the right wing's national support has not yet been tested.