Six months ago, Asghar Khan, Pakistan's most distinguished political leader not now behind bars, visited Shah Mohammed Reza Pahlevi in Tehran.

"What do you think of Afghanistan?" the shah asked.

"Pakistan's relations have never been better," Asghar Khan assured him.

The shah shook his head. That was not what he meant. Afghanistan's president Mohammed Daoud, is getting old, the Shah said. Disturbing elements are at play in the country, he added.

The shah's forebodings have now become reality. Daoud, a key to stability in Afghanistan, has been machine-gunned to death. The shah's "disturbing elements" are in power.

The analysts are left with three questions:

Will the new government of Nur Mohammed Tarika confound Afghanistan's history and became an outright satelitte - as opposed to friend - of

Will Tarika deem it wise to maintain peaceful relations with his country's non-Communist neighbors - Iran and Pakistan - or will he arm and inflame their Pathan and Baluchi tribesmen?

Will the Soviet Union continue to work for stability in their region, or will it be tempted to stir up secessionist tendencies among the Baluchis with potential prize of control - through a proxy - of a warm weather port, or a Persian Gulf tanker outlet to the sea?

These questions worry analysts here and in Pakistan, who fear that the Soviet Union is now in a position to touch off trouble from the Khyber Pass to the strategic north rim of the Arabian Sea.

No responsible expert, either here or in Pakistan, is yet ready to assert that the Soviet Union was behind the coup that deposed and killed Daoud.

There are enough internal tensions and rivalries in that impoverished and inhospitable land to have set off last week's events.

The Soviets, moreover, have played an exceptionally cautious game in the region and have made a notable contribution to the peace that now exists. Whether more adventurous bureaucrats, in uniform or out, will not be tempted to reverse this policy is known to worry both the Shah and Gen. Mohammed Zia ul-Haq, Pakistan's new strongman ruler.

The speed with which Moscow recognized the new government in Afghanistan, and the Communist affiliation of its new premier, suggest that Moscow is not unhappy with the course of events.

To be sure, the analysts caution, Moscow, with three Soviet republics bordering Afghanistan, has a strong an interest in a friendly neighbor as the United States has in good relations with Mexico.

The coup could mark a turn in Moscow's fortunes in the subcontinent. Moscow lost a good friend in India when Indira Gandhi was beaten at the polls by Moraji Desai. Both, of course, profess to be "nonaligned," but Gandhi was nonaligned toward the Soviet and Desai toward the Americans.

Another leader on the subcontinent with no great love for Washington, former Pakistani Prime Minister Zulfiqar Ali Bhutto, now faces the hang-man's noose. He was deposed by Zia, who has twice trained in the United States and admires things American.

Both Bhutto and Zia proclaim "positive nonalignment," but Bhutto seemed more positively disposed toward the East, and Zia appears to feel more positive about the West and conservative Islamic nations.

Another sensitive problem exists in the fiercely independent tribes who spill over Afghanistan's borders with Pakistan and Iran.

The experts stress that the tribesmen, Pathans in Pakistan's North West Frontier and Baluchis in the south, do not lend themselves easily to anyone. The British never did fully subdue them. Those in Afghanistan are separated from their brothers across the Pakistani and Iranian borders, and secessionist movements have plagued both countries.

Bhutto's response was characteristic. He sent in six divisions and Gen. Tikka Khan to subdue them. At the same time. Bhutto locked up the tribal political leaders of the two provinces involved, the Northwest Frontier and Baluchistan.

The late President Daoud of Afghistan complained bitterly to the United Nations. His radio and Bhutto's waged a heated propaganda war.

Interestingly enough, the Russians first urged Daoud and Bhutto to settle their quarrel. So did th Shah, a big aid giver to both and a man whose own Baluchis have made separatist noises.

Whatever his domestic failings, Bhutto was a man of peace - toward India, Bangladesh and Afghanistan. He offered Daoud emergency aid after a flood and earthquake, won himself an invitation to Kabul in 1976, and patched up the quarrel with Afghanistan.

Zia's coup last July completed the job. He pulled the "occupation" troops out of Caluchistan and freed the politicians that Bhutto had left sizzling in steamy cells.

Until last week, Islamabad and Kabul were agreed that neither would stir up the other's Pathans and Baluchis. The secessionist issue and disappeared from Pakistan's politics.

A Moscow irked by its recent string of setbacks in South Asia might, if it wanted, encourage Afghanistan's new rulers to shatter the fragile stability the region currenly enjoys.