During the XXXVIth session of Church of South India Synod, Reuben Mark has been elected as Deputy Moderator for the triennium 2020-2023 succeeding V. Prasada Rao.

[8] After the completion of graduate studies in Hanumakonda, Reuben Mark discerned his avocation towards priesthood and became a ministerial candidate of the Diocese of Karimnagar of the Church of South India, then under the bishopric of G. B. Devasahayam, CSI who took him into the Church and became his Spiritual Confessor and sent him for spiritual formation to the United Theological College, Bangalore, where he studied Bachelor of Divinity degree from 1984 to 1988[9] under the Principalship of the Old Testament Scholar, E. C. John, CSI and was taught by faculty that comprised G. D. Melanchthon, AELC[9] James Carl, SALC[9] Theodore N. Swanson, ELCA, D. N. Premnath, CSI and others.

Reuben Mark was awarded graduate and post-graduate degrees by the Senate of Serampore College (University) during the Registrarship of D. S. Satyaranjan, IPC.

After a period of teaching ministry at the near-ecumenical Seminary in Secunderabad, Reuben Mark was again sent by his Bishop S. John Theodore, CSI for research studies at the University of Copenhagen Faculty of Theology, Copenhagen, Denmark where he researched from 2000 to 2004 on the theme, A Homiletical analysis of the Revival Sermons of D. G. S. Dhinakaran and its Relevance of the Dalit Perspective[10] and later transferred himself to the Sam Higginbottom Institute of Agriculture, Technology and Sciences, Allahabad researching under the able guidance of Prof. V. K. Singh[10] and was awarded the doctoral degree in 2009.

During the period when Reuben Mark was teaching at the Seminary in Secunderabad, the Diocese of Karimnagar saw the change of at the Bishopric in 2007 following which P. Surya Prakash, CSI, Reuben Mark's Professor at Bangalore was consecrated as the fifth Bishop - in - Karimnagar who occupied the Cathedra up to 2014 until his resignation on account of superannuation resulting in sede vacante.