It's a Thai restaurant. Just get a big ol' veggie dish, avoid the soy crap altogether, ask that they don't serve you rice, and have some tea.
And most of all enjoy your friends company.
If you want to warn your friend about soy, do it before or the day after the meal.
Perhaps it is just me, but I don't see why this is complicated. Granted it blows your carbs out, but if you are avoiding grains, starches, soy and excess sugar then just right it off under 80/20.
And next time you tell your friend you are going to the "all you can eat rib shack", the one down the street where they hose down the tables after every meal... :-P
Once you learn that you create your own reality and that you are fully responsible for your life, you can begin to see the world as it is and then you realize the limitless possibilities.