There could be Two (or more) possible reason for this:
All the word "read" is in past tense
Read while Offline
Your friend was connected to net, but whatsapp was closed (not in foreground) and recieved your msg.
Then he got disconnected with internet, and while this, read your message.
Thus the Whatsapp application registered that the user has read the msg.
Then your friend got connected to internet, it is now when Whatsapp fires the "msg read by user" request to server.
But as the Whatsapp is closed, the
last seen does'nt change.
The second possibility is that your friend is using a modded Whatsapp version called Whatsapp Plus (discontinued for now).
It has the ability and option to hide
last seen of the user, even when the user is connected to internet and Whatsapp is running in foreground.
Thus, the user can chat with you in real time without changing his
Now the thing is that, Whatsapp Plus also has an option to Hide Blue Ticks and Hide second tick.
Thus, we can conclude that, it is possible, that your friend has Hide last seen enabled, and rest all disabled.
Leading to the situation in Question.