Funny you should ask since I'm sick and that's my ultimate comfort food.
However, it's doubtful. The best advice I can offer is to do a google search for Tom Kah soup and then look at at least 4 that offer nutritional values so you get a rough idea of the carb content. As I recall, it's relatively high.
Leenie - didn't you post a recipe for low carb tom kah soup a few months ago? I think it got lost in the great crash of '04. Can you post it again?