This paper explores translation strategies of a Netflix documentary series, Our Planet (2019), based on a contrastive analysis of the original narration and the Korean subtities. The thematic choices of the source text is contrasted to the first mentioned elements of the target text to examine the possibility of any congruency or discrepancy. The results are presented in three sub-topics - reference to the actor, transformation of thematic themes, integration of theme and rheme. Multiple translation strategies are illustrated throughout the subtitle excerpts that include cases such as added topical themes, omitted textual themes, added textual themes, reconstituted textual themes, pre-processed textual themes, and integrated theme and rheme. The last section demonstrates how the readability of subtitles can be enhanced by matching the original theme with the first mention in the translated clause. The findings of this study can be of practical use for AVT instructors, students, and novice translators who aspire to create subtitles of improved readability and effective condensation from the perspective of thematic structure.