To be eligible for the Diploma degree at R.D.B. College of Education in Thanjavur, applicants must meet certain criteria. Firstly, candidates should have completed their higher secondary education or its equivalent from a recognized board. Secondly, they should have obtained a minimum aggregate score of 50% in their qualifying examination. Additionally, candidates from reserved categories may be eligible for relaxation in the minimum percentage requirement as per government regulations. It is important for applicants to note that meeting the eligibility criteria does not guarantee admission, as selection is based on merit and availability of seats.