Defence Minister Ng Eng Hen wrote a personal letter of condolence to Major Soulixay Phichit, the son of Laos' Deputy Prime Minister and National Defence Minister Lieutenant-General Douangchay Phichit, on Sunday.
Mr Douangchay and his wife Mrs Thanda Phichit died in a plane crash in Laos the day before.
In the letter, which was released to Singapore media, Dr Ng wrote: "My wife and I were deeply saddened to learn of the passing of your beloved parents.
"We had just met up with them a few weeks ago in Hawaii where the defence ministers gathered for the Asean-US Informal Defence Ministers' meeting.
"We enjoyed their friendship and I admired your father's dedication and commitment to his responsibilities at the Lao Ministry of National Defence."
Dr Ng said his death was "a great loss to Laos and the Lao Ministry of National Defence".