On the other hand, though, my first thought was, "How cool is it that Tessa speaks enough Thai to explain the program, even if haltingly?!" I can sort of relate to your experience because your Thai sounds like my Malay, in which I can go on for a few minutes in the language, but at some point, I have to engage my mental "translation engine" because I just don't have the vocabulary to do it in Malay. And that additional purposeful effort makes it harder to maintain my train of thought, which is when the fumbling begins.

But I think we still get away with it because, in our societies, English is the prestige language. And with most of the materials needed to get better in our craft being written in the English language (with limited translations), it's easy to get stuck in that English-speaking bubble. Now that you mention it, I'm wondering if being halting in our native tongues might actually be taken as an indicator of competence in our fields, because it might be seen as a sign of being fully absorbed by our work...