Former vice president Walter F. Mondale's new neighbors in this secluded, wooded, upper-class, solidly Republican suburb of the Twin Cities have a message for the Democratic presidential aspirant and his wife, Joan:

"Please Do Not Disturb."

North Oaks is an extremely private surburban enclave about six miles due north of the St. Paul city limits, and its residents figure they've got to draw the line somewhere. They are wary of Mondale--who bought a $200,000, four-bedroom home at 4 Thrush Lane here last week--and the attendant undesirables of a presidential campaign such as the media, Secret Service and sightseers.

How private is North Oaks? It is so private that uninvited motorists on the roads are legally trespassers. It is so private that it refuses government road money so the government can't force the suburb to open its roads to public access.

Part-time Mayor Warren Johnson made it clear that the 2,880 residents want to keep it that way. He recalled the Secret Service restrictions, media turmoil and traffic jams around Ronald Reagan's Pacific Palisades, Calif., residence while Reagan was making his way to the White House.

"Look at what Carter did to Plains, Ga.," Johnson said.

Johnson, director of corporate planning for Micro Components Technology Co. in addition to being mayor of a community where the median annual income is more than $53,000, doesn't object to the Mondales' purchase. He said North Oaks was honored.

But at the time of the purchase Johnson mailed a cautionary letter to Mondale asking for a kind of mini-summit meeting to work out potential problems. As of yesterday, the mayor had received no reply.

"I am concerned," he wrote, "that your political prominence may result in activities and pressures that may create situations that we are not prepared to handle or accept."

Johnson said that he had the obligation as mayor to "continue the rustic, private concept of our village, and it is in that vein that I initiated this correspondence."

In an interview, he explained that he was afraid primarily of an influx of curiosity-seekers driving hither and yon to get a glimpse of the Mondale residence.

"This is a private village," Johnson said. "Basically, you have to be invited."

The suburb--not quite nine square miles, of which almost one-fifth is lakes--can shut out the rest of the world because areas that are public elsewhere are owned here by a "private association," to which all residents belong and pay $265 in annual dues. The association owns the recreational areas and the roads; federal and state grants are rejected to avoid any possibility that governmental money would force freedom of access for outsiders.

Signs warn away trespassers, and until two years ago there were gates at the entry points. The mayor noted that trespassers could be arrested or stopped at the village borders.

The concern about disruption of North Oaks' rustic way of life doesn't appear be partisan, although the Carter-Mondale ticket lost in North Oaks to the Reagan-Bush ticket, 1,249 to 338.

One of Mondale's reasons for buying into the community was to get away from campaign trail stress, as well as to have a place to entertain hereabouts. It isn't clear, however, whether 4 Thrush Lane is envisioned as a "Minnesota White House," nor is it known how much time Mondale will spend in a place he and his wife bought sight unseen on friends' recommendation.

In Washington, the Mondales live in Cleveland Park, maintaining a voting residence at Joan Mondale's parents' home in Afton, Minn.

For the present, the house here is to be used by their son, Teddy, 25, a University of Minnesota student.