Your situation doesn't allow a companion (see link Guvner067 posted), judging by the same page (Lounges worldwide tab) it looks like you will be in the Royal Silk Lounge. I'd inquire with Thai Airways if you can buy access to this lounge for a companion. Keep in mind the complaints many people have of the TG lounges, and consider if lounge access is really worth it.
Or you both buy lounge access in Louis Tavern, I guess. But thats also a pretty sad lounge imho.