My favorite greasy hole in the wall is this green garage like space with picnic tables and food served in to-go styrofoam boxes called Bangkok Chef. Cheap. Tastes like that yummy carcinogenic burnt part of the pan that gets encrusted on your food.
1627Nuuanu Ave, Honolulu 96817
If you're looking for a casual sit down place that uses real bowls and utensils, there's Siam Garden Cafe.
1130 N Nimitz Hwy, Honolulu 96816
And for curries, noodles, rice plates and salads Phuket Thai in the McCully shopping center is another place to try.
1960 Kapuolani blvd unit 109