From India -- gentle comedy; Malgudi Days, by R.K. Narayan. New York: The Viking Press. 246 pp. $14.95.

The Indian writer often mentioned as a Nobel Prize candidate is, in some ways , a latter-day Dickens or Twain -- a master of vernacular comedy who substitutes for his great forerunners' passionate social consciences an unruffled tolerance for human folly and belief in essential human goodness.

In this new collection -- a distillation from two earlier books, with several longer later stories -- Narayan displays his virtuosic understanding of character. The denizens of his fictional Southern Indian town whom we come to know intimately include assorted students, tradesmen, householders, and criminals; the mailman who ''allowed himself to get mixed up with the fortunes of the persons to whom he was carrying letters''; ''the oldest man in town,'' oppressed and annoyed by the ceremonies devised to honor him; even guard dogs and cobras impress us instantly with their vividly rendered personalities.

Narayan always writes wonderfully (in English); but it must be admitted that his plots are often thin, and overrely on coincidence or contrivance. One splendid exception is the recent story ''Second Opinion'' about a semi-dutiful son dominated by his widowed mother. The individual stories seem less striking than does ''Malgudi Days'' considered as an organic whole -- a gallery of fascinating people which expands into an authentic human comedy.