Thailand now has four sites under this category after Ban Chiang was added in 1992, and the historic cities of Ayutthaya and Sukhothai in 1991.
Environment Minister Phatcharavat Wongsuwan said he was delighted to hear that the ancient town was chosen by the World Heritage Committee at its meeting in Riyadh, Saudi Arabia.
“It’s an honour for Thais,” he said, adding that it will enable people to preserve natural resources as well as stimulate the economy and tourism.
He also thanked relevant agencies for their work in promoting Si Thep internationally.
This archaeological wonder, which is believed to date back 1,700 years, was proposed to Unesco in 2019.
The remnants of the city are located on 4.7 square kilometres of land in Si Thep district, about 200 kilometres northeast of Bangkok.
It was home to a late prehistoric community before becoming an important town in the Dvaravati or Mon Kingdom era (1,400-1,000 years ago). It then flourished for the next 200 years during the Khmer Empire before being abandoned.