Thai police arrested two men on charges of smuggling African ivory into the country to supply shops in Thailand that sell jewellery and trinkets, including to customers in the United States, authorities said.
Police said the arrests were the result of Thai efforts to more strictly enforce wildlife protection laws - amid concerns Thailand has become a hot spot for a growing illicit ivory trade in Asia.
The UN Convention on International Trade in Endangered Species banned all international ivory trade in 1989.
"Thailand has been criticised for neglecting wildlife trafficking," said Colonel Seubsak Chavalviwat, deputy commander of the police's Natural Resources and Environment division. "We had to step up and get more strict on these crimes."
Undercover officers purchased ivory from Samart Chokechoyma, 36, and Kanokwan Wongsaroj, 38, and DNA tests showed that it was of African origin, he said.
"We have evidence they were selling illegal ivory on the internet to a customer in the United States," Mr Seubsak said, without giving details.
The US Fish and Wildlife Service, which has been working with Thai authorities for the past two years, welcomed the arrests.
"Monday's arrests are significant in that they remove two more players from a global black market that threatens the survival of Africa's elephants," agency spokeswoman Tamara N. Ward said in a statement.
"This case also spotlights the importance of international cooperation in efforts to shut down illegal wildlife trafficking."
Steve Galster, the director of Freeland, a group dedicated to stopping the illegal wildlife trade, said the arrests showed authorities were starting to catch up with dealers who have operated with impunity in the region for years.
"This was a big success because the Thais have been looking at a lot of ivory coming into this country for the past couple of years," Mr Galster said.
But he said the arrested men were just middlemen and police need to find the masterminds.
The 1989 ban did not address domestic trade and smugglers have increasingly turned up in Thailand, where Mr Galster says they routinely sidestep the ban by mixing African ivory with those from domestic sources and then claim it all comes from Thai elephants - a tactic that is effective because it can be difficult without DNA testing to tell the difference between African and Asian ivory.
They have also benefited from lax law enforcement and weak laws in Thailand. Among the quirks is a vague Thai law which makes it difficult to prosecute a vendor once the ivory has been crafted into statues or other products, Mr Galster said.