Then go for distance education.Go and search for distance education courses.Nad apply to them and get admission.After admission you can continue your job and education paralley.

Hello,
You can't get good jobs after doing only diploma in mechanical engineering.You have to do lateral entry btech course for more job related options.However,if you want to do a job and continue further studies then you may opt for distance education course of btech lateral entry.Try to find out the name of such colleges.
Good luck.

In my opinion, after completing diploma do btech then go for job