Laundered' elephants
Traffic and other campaigners want to see a toughening of the laws in Thailand. If an animal is captured at the border it can be seized.
However, if the animal gets into the country there are significant loopholes. Elephants don't have to be registered until they are eight years old, creating an opportunity for these smuggled calves to be "laundered" into the domestic population.
"Elephant populations are being depleted all over South East Asia," said Dr Shepherd.
"By logging, being poached for their ivory and captured for trade - if you add up all these pressures, any off-take at all has a conservation impact."
Political turmoil in Thailand over the past two years hasn't helped the drive to strengthen the laws in the country.
Thailand made significant efforts to ban a legal trade in ivory ahead of a meeting of the Convention on the International Trade in Endangered Species (Cites) last year.
There are worries that while laws exist on the statute books, they are not always enforced.