For centuries kings of Thailand ruled the country according to these principles. They allowed subjects to voice complaints.
Dharma has never been out of date.
His Majesty the King's sufficiency economy principles are based on the Buddha's "Middle Path" of moderation, Surayud said.
The United Nations Develop-ment Programme's report on the sufficiency economy theory is proof the principle is suitable for the time, he added.
This is the third year Thailand has hosted United Nations Day of Vesak (Visakha Bucha Day) celebrations.
The theme of this year's International Buddhist Conference is contribution to good governance and development.
Meanwhile, higher learning is on the agenda. Buddhist universities in China, Vietnam, Cambodia, Thai-land and elsewhere will form an association.
This morning, world-famous Zen master the Most Venerable Thich Nhat Hanh delivers an address on the Buddhist contribution to good governance and development.
In the afternoon, monks from around the world join a chanting ceremony at the Temple of the Emerald Buddha to invoke blessings upon His Majesty King Bhumibol Adulyadej in the year of his 80th birthday.
Monks and scholars from 61 countries are participating in the International Buddhist Conference on the United Nations Day of Vesak at the UN Conference Centre.
Five thousand monks attended its inauguration at Buddhamonthon in Nakhon Pathom on Saturday.
Meanwhile, many participated in Buddhism Promotion Week events at Sanam Luang yesterday.
Homage was paid to Buddha relics. Other activities included sermons, exhibitions and a drawing competition.
The event continues until Thursday.