See there are no Online Diploma programs available in Psychology. You can do certification programs in Psychology from different institutes online but Diploma program isn't available online. To know more about the Certification program in Psychology offered by different organizations visit the link below:

https://www.careers360.com/courses-certifications/psychology-courses-brpg

Some of the top colleges for Diploma in Psychology (Full Time) visit the link below:

Bhonsala Military College, Nashik

Amity University, Lucknow Campus

BSSS Bhopal - The Bhopal School of Social Sciences

Santosh Medical College, Ghaziabad

Sweekaar Academy of Rehabilitation Sciences, Secunderabad

Sri Ramakrishna Mission Vidyalaya College of Education, Coimbatore

For more colleges visit the link below:

https://university.careers360.com/colleges/list-of-diploma-in-psychology-degree-colleges-in-india

To know more about Psychology visit the link below:

https://www.careers360.com/courses/psychology-course

I hope this answer helps. All the very best for your future endeavors!