Well, he is not there in his personal capacity as the Twitter account is being managed by the Prime Minister’s office in New Delhi.
(The account is not verified yet… But it looks pretty legit).
The account already has around 5200 followers and it has sent out three tweets.
There is no information on whether we would see Dr. Singh tweeting himself (like Barack Obama does sometimes in USA).
You can subscribe to the account here:
Here is the Twitter feed: