Former Singapore ambassador to Japan Chin Siat Yoon is capping his more than 40 years of public service with one of the nation's highest honours.

Mr Chin, who retired in June, is one of two recipients of the prestigious Distinguished Service Order this year.

The father of three, who turns 68 this year and was ambassador to Japan from April 2012, said he was "honoured and deeply humbled" to receive the award.

"It was somewhat overwhelming. When I told my wife Lee Moi, she was happy for me. My daughters, who are all overseas, also thought it was 'cool'," he said.

The Colombo Plan scholar began his career in the SAF as an army officer in 1972 and later held numerous key appointments, including that of assistant chief of the general staff (logistics) and assistant chief of the general staff (intelligence).

With the formation of the Joint Staff in 1984, Mr Chin became the first director of the Joint Intelligence Directorate. He held this appointment, with the rank of brigadier-general, until he left for further studies at the Johns Hopkins University in the United States in August 1989.

Throughout his career, Mr Chin also served on the boards of directors of various statutory boards and companies.

In July 1990, he was seconded to the Ministry of Foreign Affairs (MFA), and he retired from the SAF in December 1995. While at the MFA, he served as ambassador to Thailand from September 1990 to December 1994, with concurrent accreditation to Myanmar and Cambodia.

From January 1995 to July 1996, he was Singapore's trade representative in Taipei, and later became ambassador to Germany from August 1996 to December 1997.

Besides today's award, Mr Chin was also awarded the Public Administration Medal (Silver) (Military) in 1981, the Public Administration Medal (Gold) in 2000, and the Meritorious Service Medal in 2006.

For his role in promoting bilateral military relations between Singapore and Indonesia, Mr Chin was awarded the Bintang Yudha Dharma Pratama ("Star of Honour" - Second Class) by Indonesia in 1989.

Looking back at his career, Mr Chin said he felt a profound sense of gratitude at having been given the chance to serve Singapore. Before his post in Japan, he served as ambassador to China from February 1998 to March 2012, and was Singapore's longest-serving envoy there. He said it was his stint in China that left the greatest impression: "China is a vast country. And you could feel that it was on the move."