THE LATEST headline -- "18 More Korean Dissidents Held as Unrest Spreads" -- conveys the disquieting impression that little has changed in South Korea since longtime dictator Park Chung Hee was assinated a month ago. Despite the promise implicit in his departure from the scene, martial law remains in effect, students and others are demonstrating, and the government is rolling them up. One of the former president's most diligent yes-men, moreover, is about to be elected interim by the same Park-appointed body that anointed Mr. Park last year.

Yet a lament is almost certainly premature.Under a surface designed to make others (in particular, North Korea) feel that post-Park Korea remains united and strong, South Koreans are moving with no little vigor to adjust their political system to the realities and needs of the more developed and better-educated society that South Korea has become. There have been arrests of some of those who are actively testng the new possibilities for opposition and dissent, but there have also been releases -- of longtime political prisoners, though not yet of the leading opposition figure, Kim Dae Jung, and a number of the newly arrested. The pattern is erratic enough to indicate that the junts currently in charge is not of one mind.

Most important, the pro-government party has taken a conciliatory stance to the political opposition, and not just in a symbolic way. It has, for instance, offered equal respresentation on the commission set up to redraw the constitution that President Park had imposed to suit his own disctorial style. All this goes on within the context of a military government that can take back with one hand what it gives with the other. There is also some critcism of the military's decision to elect an interim president under the old constitution rather than rewrite the constituion first. This was done in the name of stability, a goal often used in the past to justify excesses. Yet we have the impression that, however nervously and raggedly, South Koreans are trying to move in the direction of more representative rule.

The signals they are getting from the United States, their chief patron and protector, are not so easy to pick up on the public screen. This is probably the way it ought to be. The United States has a strong desire and interest in seeing Seoul turn toward democracy, and some Americans fret that the administration is not getting out front in this regard. Yet conspicuous intervetion can be self-defeating. This is a time for discretion.