@nghosh: It is not necessary to pursue M.Tech as a Govt. Assistant Engineer. You will never get any financial benefit.
By the way, in which stream you pursued your Bachelor’s degree?
You can go for higher study for better opportunity. But I have serious doubt whether Govt. will allow you to go for a full time masters degree. In that case, you may go for masters degree at Jadavpur University (Evening Session). Govt. shall give you NOC in such case. Contact JU for more details.