The present case study explores the assessment practice of two examiners from different academic backgrounds on an undergraduate thesis work in mathematics education. Reflection notes and feedback from two instances of a thesis-writing process are interrogated using a framework based on a semiotics perspective to meaning-making. It is shown that the examiners utilize aspects that are 'immediate and non-contested' to successively make accessible that which is 'withdrawn yet to be revealed.' In this process, varied interventional approaches are observed to support desirable aspects of teacher professional knowledge including critical-analytical disposition. The study also highlights knowledge integration for teaching, scientific disposition, collaboration, and knowledge transformation as some of the desirable aspects of teacher professional knowledge. The findings indicate that knowledge integration and transformation remain an issue of concern for pre-service teachers. This raises the question of how desirable traits for a teacher-as-a researcher can be promoted within the context of thesis work.