A lot of valid criticism here about the measure of complexity, but considering the author’s initial motivation, I think the approach makes sense: “The magazine had a little travel article, and it was written in English on one page and Thai on the other. The Thai version was so much shorter that I started to wonder if it was more efficient.”
If the goal is to identify which language would have produced the most subjectively visual “short article” per the description above, the approach sounds ok. For example, concerns with serifs, variations in character sizes, the information content of characters, etc become moot because they contribute to visual clutter and typography, which the author would want to count against the language.