President Reagan telephoned Christmas greetings to members of the armed forces serving abroad Saturday and lamented the crash of a Pan Am jumbo jet in Scotland as "a tragedy words can hardly describe."

The president, who is vacationing at the home where he and first lady Nancy Reagan will live after he leaves office Jan. 20, also received thanks from an official in Lockerbie, Scotland, for his expression of condolence to people in the community where the plane crashed."On behalf of the people of Lockerbie I think you and the first lady for your kind wishes at this time of sorrow," Francis Park, the convenor of the Annandale and Eskdale District Council, wrote to the president. "Our small community has suffered much, but our sadness is even greater when we think of the loss of so many people from the United States. Our thoughts are with their friends and relatives wherever they may be."

One of the servicemen Reagan called, Petty Officer 1st Class Marc Redshaw, boatswain's mate on a Coast Guard patrol boat based in San Juan, Puerto Rico, is an English-born naturalized American.

"I noticed you were born in England and both countries this weekend are saddened by a tragedy words can hardly describe," Reagan told Redshaw. "The sorrow and loss for so many weighs on our hearts and I can only pray that the spirit of peace which is Christmas will find its way to comfort all of us."

Reagan also telephoned Specialist Christopher M. Skezas of Bonita, Calif., a soldier on duty with the Multinational Force and Observer Detachment in Egypt's Sinai Desert; Airman 1st Class Richard E. Green of Washington, a food service specialist at Shemya Air Force Base, Alaska; and Lance Cpl. Jeffery D. Tidey of Trenton, N.J., a Marine Corps radio operator on duty in Panama. He planned to call a Navy seaman in the Far East later in the day.

He told all of the servicemen, "We deeply appreciate your service. It's a sacrifice we recognize - especially to be away from home at Christmas. Please tell your fellow soliders we are thinking of them. Our Christmases are brighter and better because of what you're doing on the frontiers of freedom, making it safer for everyone here at home. God bless you. Carry on."

Earlier, the president extended special Christmas remembrances to homeless children in America and to victims of the earthquake in Soviet Armenia.

Although the president's talk was taped on Thursday, after the Pan-American jumbo jet crash in Scotland, he made no mention in his broadcast of the crash, which killed all 258 passengers and crew and a score of others on the ground.