The monarch, who has strained her back and has also been resting for nearly a month after preliminary tests in hospital, welcomed the Vietnamese ambassador Nguyen Hoang Long via video link.
Seated in her Oak Room sitting room at Windsor, the 95-year-old head of state could be seen on the computer screen on Thursday wearing a turquoise dress, with black collar detail, her pearl necklace and a brooch.
The ambassador, who was at Buckingham Palace with his wife Vu Huong Giang, presented his credentials, and the letters of recall of his predecessor.
On Wednesday, the monarch was seen for the first time since she cancelled her Remembrance Sunday appearance, when she held a face to face audience with the outgoing head of the armed forces General Sir Nick Carter.
The nation’s longest reigning monarch told the military chief it was “easier to continue” once you get into the top military job.
She was pictured standing and was without a walking stick after spraining her back, which forced her to cancel her appearance at the Cenotaph for the national ceremony in honour of fallen servicemen and women.
She also held a virtual audience on Wednesday with commanding officers of the Royal Scots Dragoon Guards.
The head of state has been carrying out light duties only after being admitted to hospital on October 20 for what was her first overnight stay in a medical facility in eight years.
Concern for the Queen’s health has increased as she has continued to cancel engagements.
She missed a two-day trip to Northern Ireland, and was not able to attend the Cop26 climate change summit, the Festival of Remembrance, Remembrance Sunday and the Church of England’s General Synod.
She has no other major public engagements planned before the end of the year.