THE UNITED STATES provided a quota for 168,000 refugees from Indochina in this fiscal year, but now the mood is changing and there are signs everywhere of diminished receptivity to a continuing flow. Members of an American congressional delegation visiting refugee camps in Thailand, for instance, suggested the other day that American law and policy alike have been too liberal. It has become commonplace for communities in the United States to indicate that they feel put upon by refugees, from Indochina and elsewhere, who compete with American citizens for work, living quarters and social place.

Unfortunately, although the mood is changing in the United States, the flow of refugees is not changing that much in Indochina. An advisory panel named by the State Department has just reported that an "ongoing, substantial exodus" is likely and that the harsh living conditions, the fighting and the political oppression in Indochina indicate that "many thousands will flee every year . . . for many years to come."

What is shaping up is a very painful situation. The nearby Asian nations that have been the places of temporary "first asylum" for many Indochina refugees, both those fleeing by land and those fleeing by sea, can observe the United States and other areas of permanent resettlement cutting down their welcome and, in anticipation, they are already raising their barriers against new entrants.

One result is to turn the attention of those most concerned with refugees to what has been up to now the relatively overlooked question of "humane deterrence." If resistance to asylum and resettlement is growing, what can be done in an acceptable way to keep those who would otherwise flee at home? In the same spirit, it is being asked whether the United States may in some respects be inadvertently encouraging departures of people who, without such encouragement, would not become refugees.

Does the very existence of asylum and resettlement programs and refugee quotas "pull" out people who would not otherwise be "pushed" out? Do Voice of America broadcasts include in their portrait of American life a fair rendition of the uncertainties facing refugees during flight and even after arrival?

It is not always easy to keep an edge of smallness or meanness out of these questions, but they are legitimate questions. They are legitimate, that is, as long as they do not become alibis for denying relief to people to whom the United States owes an abiding obligation by virtue of their association with this country in the Vietnam war or by virtue of their ties with kin already living here.