Possibly a Trimeresurus macrops (Large-eyed Green Pit Viper) - Northern and Central Thailand and often found around Bangkok, they reach a length of around 50cm... Only a guess of course...

What is the name of this snake
 

Hi
I like to know the name off this snake. It is a viper. I also like to know from whichs area it comes from.

Woongson

It's an Ahaetulla nasuta (Long-nosed Whip snake)Thai: (ngu kieo pak nab)It can have a length of 190 cm found in the North, north east and central Thailand.The colour of this species varies from grass green to grey, brown or yellowy.
They are very active during the day, live in trees and bushes on agricultural land and woods.They feed themselves on frogs, lizards and rodents.
Although this is a type of rearfanged snake, there is no danger to humans. The venom must be massaged into the bite wound with chewing movements in order to be effective. Even when preying on small lizards, the poison needs 15 minutes before being affective.
Looks like you're having one as a pet hobby.Where you get it from?