I think the best Thai grocery around is on Middletown Ave./Rt.80 in Foxon. They specialize in Thai/Malay foods. I'm not sure of the name, but its in a very little strip mall on the right hand side going east, I think there's a Dominos pizza around the corner in the same strip. Just past the diner on the opposite side.
@chefstu Are you thinking of Asia Grocery Store, at 20 Foxon Boulevard?
If so, +1 to that.
One of the ways I respond to New Haven naysayers is to point out that we may not have tons of Asian groceries, but we have one especially for Chinese, one especially for Japanese, one especially for Korean, and one especially for Thai. Not to mention the handful of South Asian markets.
Asia Grocery Store
20 Foxon Blvd, New Haven, CT
This is just out of your requested area but "Indian and Asian Groceries-Market" in West Haven is not far away. I do not know the store, I just have it in my data bank. Their website is not helpful, but perhaps others can comment. Also, there's a phone number.
315 York St., West Haven, CT 06516 (203) 934 9676
BTW, in New Haven I have been disappointed in the variety and selections in the two stores I know. I am glad to hear about the one in Milford.
There's a large Asian market in Milford. I believe it's called Lin Asian Market. If you're on Route 1 heading towards the mall, just past Colonial Toyota and Xpect, same side of the street (left), is a big sign for their store. It's right past the 7-Eleven (on the right). They have Thai basil, the little eggplants and tons of other stuff. I just love the store.