Traffic, which monitors such activity, said many of the species, despite having international protection, were not native to the country, and so trading them was unregulated.
The listings were found on 12 Facebook groups during one month in 2016.
Facebook said it did not allow the trade of endangered species.
Among the 200 different species listed for sale were two non-native species banned from international commercial trade - the Eurasian otter and the black spotted turtle.
Some of the animals for sale which are banned from international commercial trade are native to Thailand, such as the helmeted hornbill and Siamese crocodile - which are both critically endangered - and the Asiatic black bear.
Although only one helmeted hornbill was discovered for sale, Traffic said the critical status of the species meant that any number taken out of wild populations would have "serious implications" for its survival.
Traffic's findings are to be published this week in a report on the use of Facebook for animal trading in Thailand.