Speaking at the opening of the Convention on International Trade in Endangered Species (Cites), Ms Yingluck said she will amend Thai law "with the goal of putting an end to the ivory trade".
She did not give a timeframe for the amendment.
Activists say criminals exploit the kingdom's legal trade in tusks from domesticated Asian elephants to sell illicit stocks of African ivory, driving a poaching crisis that sees tens of thousands of elephants slaughtered each year.
Thailand is currently the world's largest illegal ivory market behind China, according to the conservation group World Wild Fund for Nature (WWF), with scores of unauthorised traders selling products made from tusks often to foreign tourists.
Defending her nation's commitment to protecting the species, Ms Yingluck said "elephants are very important for Thai culture", adding that "no one cares more about the elephant than the Thai people".
"Unfortunately, many have used Thailand as a transit country for the illegal international ivory trade," she added.
The premier said Thailand would establish tighter controls to curb illegal flows of ivory and ensure the existing ivory supply is from domestic elephants before legislating for an outright end to the trade.
"We're thrilled to hear that Prime Minister Shinawatra took this opportunity to seize the global spotlight and pledge to end the ivory trade in her country," said Carlos Drews, head of WWF's delegation to Cites.
But he cautioned that Ms Yingluck "needs to provide a timeline for this ban ... because the slaughter of elephants continues".
Achim Steiner, executive director of the United Nations Environment Programme, said the African elephant population is declining by 10% to 11% a year in many countries.
"We are really confronted with a crisis of the future viability of those populations ... and ultimately the survival of the species."
Since coming into being in 1975, Cites has placed some 35,000 species of animal and plants under its protection, controlling and monitoring their international trade.
The 178 countries who have signed up to the convention - and who must undertake measures to implement its decisions - will also consider growing calls for greater regulation of the shark fin trade.
Similar proposals to protect a number of shark species - whose fins are prized in Asia - have previously failed in the face of opposition from a group of Asian countries concerned about their fishing industries.
Humans kill about 100 million sharks each year, mostly for their fins, according to the UN Food and Agriculture Organisation, and conservationists are warning that dozens of species are under threat.
"We are now the predators. Humans have mounted an unrelenting assault on sharks," said Elizabeth Wilson, manager of global shark conservation at Pew Charitable Trusts.
The Cites meeting, which ends on March 14, is also looking to strengthen protection for multiple plant species, including Madagascar ebony and rosewood, from a host of countries.
The meeting is at the Queen Sirikit National Covention Center.
Read the original story on the Bangkok Post here.