THERE'S BEEN ANOTHER coup in Afghanistan or, perhaps one should say, in Kabul, since Afghanistan is one of those traditional countries, culture-locked as well as land-locked, where the regime in the capital changes occasionally but the hard lot of most of the people does not. This time the change was bloody. President Mohammed Daoud was excuted, along with perhaps hundreds of others. Unlike the last coup, which had somewhat the aspect of a family fued, this one had an ideological tinge: The new president and prime minister of the new "Democratic Republic of Afghanistan," Nur Mohammed Taraki, is identified as leader of the previously outlawed local Communist Party. The Soviet Union recognized his regime almost instantly.

We're not at all sure what Communist leadership bodes for Moslem Afghanistan. But it would be unfortunate if the Kremlin were tempted to exploit an opening for its own narrow purposes. That is not so much because Afghanistan is a great strategic prize as because it sits in a region of ethnic and national tensions and its tranquillity is important to the stability of the region as a whole. The previous government in Kabul balanced off its neighbors quite well, even improving relations with one, Pakistan, with which it shares a tribe of substantial volatility, the Pushtuns.It also continued the long-standing Afghan tradition of welcoming support from various countries worried that somebody else might achieve undue influence. Foreign aid has been a principal source of national revenue for the Afghans, who are adept at capitalizing on their reputation as a country strategically and politically in the middle. What their feudal system has been poor at is getting the aid to trickle down.

In an earlier day, the United States might have greeted a coup in Kabul with a glint in its eye, asking itself what it might do in, and for, that particular corner of the Free World. But, nothwithstanding the apparent cast of the new regime, there's little for this country to do now. Afghanistan's interest in keeping up good relations with all available partners would seem to be an enduring one. The regional states adjoining it are competent to deal with any threat to their interests that might be posed by the new crowd now in control in Kabul.