The large scaled Green Pit Viper is a genus of venomous pit vipers found in Asia from Pakistan, through India, China, throughout Southeast Asia and the Pacific Islands. Most are relatively small, primarily arboreal species. With thin bodies, and prehensile tails. They are typically green in color, but some species also have yellow, black, orange or red markings.Their diet includes a variety of other animals, including rodents, lizards, amphibians and birds.
Common name - Large scaled Pit Viper.
Scientific name :Trimeresurus macrolepis. This is a venomous pit viper species found in the hills of southern India. The type locality is listed as "Anamalai hills at 6000 feet elevation and Palni hills at 4000 ft elevation."
I saw this beauty at a place called "Grass Hills" a peak in Annamalai hills. Thinking that it is a harmless green snake - i went close and lying on my belly was focusing on it, when the forest guard pulled me by the scruff to tell me that it was a viper.
The beauty refused to come out of the grass for me to get capture it completely.
Facts courtesty - Wikipedia and bikram of TN who helped in identifying the snake.