Hello,
Yes, you can surely do a degree after diploma. There are many private colleges and universities who offers degree courses after diploma. I would like to mention about LPU as I have clear view and information about it. LPU offers a number of Lateral Entry programmes in which a student can take admission after diploma .
Procedure for diploma holders to get into other degree courses
Diploma holders who want to get admission into degree courses other than engineering should first of all select the course for which they are eligible. Then they should obtain the application form from the relevant institution by paying the application fee in cash. They should fill the form as per the instructions given on the information brochure. Duly filled forms can be submitted through post along with the specified documents and it should reach the concerned office before closing date. It is possible to pay the application fee by demand draft and send it along with the filled form. Online filling and submission is there in the case of certain institutions. In that case, fee payment can be done through credit/debit cards or internet banking.

Application forms will be short listed according to the marks obtained in qualifying examination and short listed candidates will be called for counseling. After counseling, they can join the relevant degree course.

Certain Universities like Deen Dayal Upadhyay Gorakhpur University, Nehru Gram Bharati Vishwavidyalaya etc. conduct entrance test for short listing candidates to degree courses.
For example, after doing engineering diploma, you can get into degree course into second year directly. But in an entrance based degree course having a diploma may be considered minimum eligibility and you have to go through due process for the degree admission, like in case of management or architecture.
There are many options after diploma, one can work in their field of study, otherwise you can go for b.tech degree. It will be good if you do b.tech after diploma because you have already gone through many technical aspects in diploma. In b.tech you won't be able to see that many technical things as if you saw in diploma. And one more important thing is that in normal engineering colleges you can join in second year directly and continue studying b.tech.
If you chose to go for a job after diploma , you have to work hard and when the time comes you wont be able to go for higher positions, because you don't have a higher degree like b.tech. So it's better to do b.tech.