If you want to try some street food around Hua-hin downtown, then please try the Sukiyaki Hot-pot Restaurant right on the street, near the night market. In my opinion, it is one of the best spots with a lot of customers every night.
This is not only the first street restaurant I tried in Hua-hin (2004), but also the only one place I kept coming back for so many times.
I think people call this restaurant Sukiyaki because the major menu is Hot-pot, but I don't think it's the usual Japanese Sukiyaki.
The menu has different hot-pot varieties. You can either choose seafood (fish, squid, and shrimp), or chicken, or pork, or beef, etc... Then you put them together with vegetables in a clay pot, on fire too. Normally, I always asked for some eggs, more tofu, and fish. I really love the fish here.
Besides hot-pot, this restaurant also has plenty of other good food. I don't even remember half of them. I think you should try the Thai style BBQ, the grilled fish, the simmered prawn with glass noodles, and the Thai fried rice with crab meat.
In terms of location, Sukiyaki restaurant is also a very cool place to sit at night on the street and drink beer with friends. Since Hua-hin is not hot, noisy and smoky like Bangkok, sitting at this restaurant at night is really nice.
Here is the location of the Sukiyaki Restaurant:

The crazy Vietnamese group @ the Restaurant:

Photos:
Nguyen Truong Tung