Seafood restaurants in Bangkok. No need to travel 1 hour or more.
2 more places worth visiting - the Ang Sila Fish market.
This is set along a pier with boats unloading fish at the far end - well worth a visit. They will provide you with an insulted (polystyrene) box and ice to take any purchases home in.
The mini oysters are from the beds here and shucked on the shore - so you no they are fresh. I wouldn't buy them once bagged in off stalls Bang Sean itself, just buy/eat them at the shellfish beds.
Of course virtually all the seafood restaurants are over the sea with views
Nong Mon market is famous for two things - the huge range of dried seafood (there are acres of seafood drying establishments in the area)
and
Khao lam - the sweet sticky rice baked in bamboo. This is a local speciality
You really need transport to get round all these places though. The local Song Taews are OK but difficult to work ot which one you want.