"There have been years without any real action on the ground when it comes to controlling the illegal ivory market, be it illegal imports or trade within Thailand," said Oeystein Stoerkersen, chairman of CITES' governing body.
The Geneva-based Convention on International Trade in Endangered Species of Wild Fauna and Flora has set Thailand an August 2015 deadline to fall into line.
Bangkok is under additional pressure to report back by next January on the steps it has taken to bolster recent laws that CITES claims are insufficient.
Among the species on the CITES watch-list are orchids and various species of exotic wood, both of which are significant export products for Thailand.
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"I think that is a strong signal to send to a country," said Stoerkersen.
The decision came as delegates wrapped up a weeklong CITES conference in Geneva covering a host of issues related to the trade in endangered species.
Earlier this week, CITES chief John Scanlon told AFP that elephants would be wiped out in some parts of Africa unless more countries got involved in efforts to prevent poaching and ivory smuggling.
Organised crime syndicates and rebel militias looking for ways to fund insurgencies in Africa have become increasingly involved in the multi-billion-dollar illicit trade, taking advantage of Asia's insatiable demand for ivory to use in decorations and traditional medicines.
Stoerkersen said Thailand was a "sink" for African ivory, sucking in imports bought by foreigners and exported on to other Asian countries.