Some say Naga and Dragon are from the same root, crocodile. In some Chinese depictions of dragons, artists would draw the faces like those of crocodile's. Only newer Chinese dragons would have more of lion features for a dragon's head.
 
Crocodile is one of the creatures that truly exist in real world. The main Thai literature that mentioned this creature extensively is Krai Thong the crocodile hunter. In this story, crocodiles have more than physical power, they are able to transform themselves as human beings and have many other magical powers. The main story is about relationship between crocodiles and humans from the conflict between teh 2 species, the hatred, and the love.
 
Another country which has a lot of Crododile's tales is Egypt because the country's main river, Nile, is infesdted with crocodiles.
 
Read more on different types of Crocodile based Creatures:
Gumpee Nimitr
Hayra