SOUTH KOREA, nervous about how the United States might react to defeat in Vietnam, drafted a secret plan for 1976 to influence the administration, the Congress, the media and assorted other folk who supposedly wield the levers of power.It is interesting to get now, from Rep. Donald Fraser's subcommittee, the details - though it is not yet clear what part of the plan was put into effect. What needs to be added, however, is that many countries, including the United States, run information, lobbying and intelligence operations quite like the one described in the Korean memo surfaced by Mr. Fraser. Indeed, the only questionable feature we see in the Korean plan is the suggestion that money was to be slipped to three congressional staff "collaborators." The use, in the English translation, of words like "manipulate" and "convert" to describe Korean intentions may or may not mean anything darker than the planners' effort to justify a big budget back in Seoul.

For now, in our view, Washington's Korean focus should remain on the tug-of-war between congressional and Justice Department investigators and the Korean government over the terms on which accused briber Tongsun Park should testify. The Americans, having made the case that he was acting as an agent of his government in bestowing funds and gifts on various congressmen, have demanded that the Koreans yield him up. They have so far refused. Only now is Seoul showing a hint of flexibility.

Reasonableness is overdue. Angered by Korean defiance, Congress has dug in its heels on providing extra arms to Seoul to compensate for the troop withdrawals planned by President Carter. Mr. Carter has sent Korea the message that, extra help or not, his withdrawal plans are unchanged. The return of Tongsun Park could be critical to resolution of both the basic issues that have become interwoven in this case: the integrity of Congress and the security relationship between Korea and the United States.

Some days it appears that it's open season on South Korea. The Fraser investigation, for instance, is proceeding on a track separate from the inquiries into Korean influence-peddling, but disclosures from it are easily read in the glow of those inquiries. We of the press make our own contribution to thos some what fevered state of affairs. The point is that there are high stakes as well as high principles involved in the U.S.-Korean struggle, and the one thing we're sure is not needed is a loaded, overstated view of what that conflict is about.