Hello!
Eligibility criteria for Diploma course after 10th :
Every Institute offering Diploma course has different eligibility criteria. General eligibility conditions for Diploma course are :
Candidates should have passed 10th standard from a school which comes under recognised board of education.
Candidates must have the aggregate score of 50% in 10th board exam but most of the institutions provide some relaxation in aggregate score for AP some reserved categories.
Candidates must have passing marks in all subjects in 10th standard.

I suggest you to check the eligibility conditions of particular institution you are interested in. As I've already mentioned the eligibility criteria varies for different colleges. So check the official website of the college if they have any separate conditions .

Hope I've answered your question
All the best!