[1] Kasun was born in Cudworth, Saskatchewan, and received a Bachelor's degree in English at St. Thomas More College in Saskatoon.

[5] As pastor in Edmonton, Kasun sought to increase fundraising for the local homeless population and advocated for the Sudanese diaspora to maintain celebration of Mass in Dinka and with their cultural elements so long as they followed the General Instruction of the Roman Missal.

[6][7] Kasun also work on an abuse prevention program in Edmonton, facing a backlash from parishioners for implementing "strict" rules that required windows in every room and multiple adults in Sunday school classes.

Efforts by Kasun and others led to the Archdiocese of Toronto receiving Praesidium Accreditation certifying a high standard of abuse prevention.

[12] As an auxiliary bishop, Kasun has presided over liturgies on behalf of the Chinese Canadians and Goan Catholics in the archdiocese.