Hi Daniele,
You lucky thing samui on sunday.
We loved Prego it is owened by the Amari and is Italian, some Thai, the service presentation etc are wonderful. Not sea front I am afraid.
For the vista try the Cliff in between Chewang and Lamai. Book and then you get a table at the front lovely views and great reviews.
Starfish and coffee in fishermans village has good beach front location.
You have mentioned Poppies and then there is Red snapper attached to the Regent.
go to them all ! and just the beach ones in Chewang.
Have a fab time.

__________________
Kiss
God laughs at people who make plans.