A federal judge rejected yesterday a request by presidential assailant John W. Hinckley Jr. that he be transferred to a less restrictive ward at St. Elizabeths Hospital and be allowed to leave the hospital grounds by himself one day each month for downtown visits.

Hinckley, 30, reading a statement on his own behalf, told U.S. District Judge Barrington D. Parker that he was no longer "a threat to myself or others" and deserved more hospital privileges.

"In the last three years, I have not been psychotic, delusional or depressed," said Hinckley, who was confined indefinitely to St. Elizabeths in 1982 after being found not guilty by reason of insanity of attempting to assassinate President Reagan nearly five years ago. Three other persons were seriously wounded in the same attack.

But Parker, who presided at Hinckley's trial, denied the request for more freedom after hospital officials testified that Hinckley was "substantially improved" but still mentally ill.

"He is no longer psychotic or depressive," said Dr. Joan A. Turkus, Hinckley's psychiatrist. "But he has a serious narcissistic personality disorder . . . . He still sees himself in a grandiose way."

Turkus said Hinckley lacked insight and judgment about his illness and did not seem to realize that his notoriety and the publicity surrounding his case could expose him to danger outside the hospital.

Hinckley, who in past statements has described himself as a "political prisoner," said it is that notoriety that is affecting his bid for a less restrictive living arrangement at the hospital.

"If I had committed any other crime in the world except this one, I would be on a minimum-security ward with more privileges," said Hinckley, who spoke in a clear, steady voice and looked considerably thinner than during his trial. "It is my crime and not my mental condition that is holding me back."

Hinckley said he had "tremendous remorse" for the attempted assassination, calling it "a senseless, ugly act," but said he now wanted the chance to "let me prove myself."

At St. Elizabeths, Hinckley is one of 18 patients in a maximum-security ward at John Howard Pavilion, the hospital's facility for patients who have been committed after criminal proceedings.

Turkus said Hinckley had been allowed to stroll the hospital grounds more than 20 times in recent months, but only in the company of two escorts, one of whom carries a walkie-talkie. She said officials hope to start him on a work therapy program in the next few months.

Questioned by Parker about reports that Hinckley wanted to marry another patient at the hospital, officials acknowledged the relationship but said he is not married.

Under District law, Hinckley is entitled to request his release from the hospital every six months. He last appeared in court October 1984 to ask that he be allowed access to reporters and permission to walk the hospital grounds one hour each day. Parker denied both requests.