Thai customs on Friday said they had arrested two Vietnamese air passengers after finding more than 100 kilograms (220 pounds) of ivory in their luggage on a flight from Angola.
The haul, which included whole tusks, ivory beads and shaped cubes which could be used for carving, was worth around $500,000, customs said in a statement.
It was found late Thursday in luggage belonging to a Vietnamese man and woman who had arrived in Bangkok on an Ethiopian Airlines flight from the Angolan capital Luanda, a customs statement said.
The pair were due to fly on to neighbouring Cambodia, but failed to report to the gate for their connecting journey after the discovery was made.
"They were later detained in the airport and then charged with smuggling banned items," the statement said.
Thailand is a known transit point for ivory, much of it destined for rich buyers in China or Vietnam where it is used in traditional medicine or as ornaments.
Africa has seen a sharp rise in the illegal trade in wildlife products such as ivory and rhino horn.
Up to 30,000 African elephants were poached for their ivory last year and a record 668 South African rhinos were killed for their horns, according to conservationists.
Thailand has come under the spotlight in recent months over its role in the ivory trade.
Campaigners have urged the kingdom to end its legal domestic tusk trade, which they say enables criminals to launder illegal African ivory in the country.