Thai food is one of the easiest to make ethnic foods at your home and have it taste fairly authentic. So I generally rate Thai restaurants on how does their dish they make compare to how I have had in Thailand and how I make it at home.
While the food at Thai Gourmet is edible, although greasy, my companion agreed that I could make better dishes than this. Now that does not constitute a put-down or I'm trying to say that the food sucked - it didn't it was good. (It's really hard to make Thai food poorly IMHO) However, as another poster said, they seem to know they have strong competition down the street where you get incredible food so they are trying to win on the portion size and value while the quality is not quite there.
Take the 3 star rating for what's it worth, the food is OK but there are much better places to go.