Hello there!

There are lot of opportunities after diploma and many more exams to write. After completion of Diploma, you can opt for a job or higher studies. There are a lot of opportunities for Diploma holders in both the cases.
For higher study, you can opt for engineering entrance examinations and if you want to get a government job then start preparing for the competitive exams like RRB JE, RRB ALP, state-level Junior Engineer examination, bank exam preparation, etc.
There are various job opportunities after pursuing a diploma in engineering. Some of the good colleges also offer campus placement opportunities after the programme. Various government organisations also offer roles for individuals who hold a diploma in engineering. Indian Railways, Power Grid, BHEL, Electricity Department, BEL and NTPC are some of the organizations that hire engineering diploma holders.
Some of the job oportunities include.

ISRO - SAC computer technician
DRDO computer technician
BSNL jr. Engineer
Delhi Metro assistant Programmer
Haryana Govt jr. Programmer
Rajasthan Govt computer operator
All state police computer operatorcentral engineering services (CPWD), central water commission , survey of India , MES etc - you can apply here through SSC which conducts exam for junior exam ( two tier ).

Railways - RRB recruits junior engineer through exam which it conducts every year

State government jobs : State government also recruits junior engineer.

PSU jobs : PSU like DMRC , AAI ,DDA , RITES also conducts exam for junior exams

I hope you find it useful.

Goodluck!