Venerable Dhammakiththi Himi came to Nagadeepa in 1943 and became the Chief Incumbent of Nagadeepa after venerable Somasirikiththi Thissa Himi. Then the island Tamil people called ​​Somasiri Tissa Thero as Periyasamy (Great Thero) and Dhammakiththi Thero as Sinnasamy (Little Thero). Both of them came together with the financial help of  Buddhist devotees the temple building which was estimated at Rs. 250,000 at that time was constructed at an initial cost of Rs. Also, a small Buddha statue and the Potgul Vihara were erected. A small Devala temple was also built adjacent to the Buddha statue. The foundation stone was also laid for a lodge with 5 rooms and a living room to accommodate the visiting members of the Nagadeepa Viharaya. In addition, a great service was rendered by him to the Nagadeepa Vihara.

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Not only that but also, during the construction of Nagadeepa, he did not forget to use the knowledge he knew to serve there. Therefore, he also engaged in bibliography. Baminithiya Mahasaya, Nagadeepa, Nagadeepa Poetry, Dharmakeerthi Enlightenment Letters, Buddhist Pilgrimage Stanzas, Sixteen Great Places, Sinhala-Tamil Training, Puttar Vanakkam are written by Dhammakiththi Thissa Himi. He also edited and republished books such as Prakrit Prakasaya, Prakrit Manjari, Dasakumara Charitha Vyakhawa, Padabheda Vivruthiya, Sinhala Thupavansaya, Sasanavansa Deepa Vyakhyaya. Also updated and published Seemalakkhana Deepaniya written by Welithara Wimalasara Tissa Thera. He also authored a book, The Opening of Arguments, called The Status Deepika, but failed to publish it.Apart from this, he is an expert in stanzas and verses.

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In appreciation of the great service rendered by him in this Sasana, In 1971 to the Chief Incumbent of Nagadeepa Dhammakiththi Tissa Thero awarded the post of Northern Provincial Leader by Walagedara Somaloka Tissa Amarapura Maha Nikaya Maha Nayaka Thero and leading Maha Sangha Sabha. Ven. Somaloka Tissa Thera of Walagedara passed away at the end of December 1974 and the post of Chief Incumbent was conferred on Ven. Dhammakiththi Tissa Thera.