Bangkok on or near the river
My wife and I will be in Bangkok later in the month, but, unfortunately, it is only for a stopover on the way home from Laos. We will be staying at the Peninsula Hotel and would like to have a good Thai meal, but not too far afield, because we have an early flight the next day. I have read some nice things about the Supatra River House and Khinlom Chomsaphan, but would love some input from some fellow chowhounds.
I haven't been to Supatra River House so I have no comment on it.
Khinlom Chomsaphan food is good. You should have a good time there. One thing to keep in mind, if you're planning for a dinner there on a weekday, traffic from Peninsula to the restaurant could be an exhausting experience one.
There is Yok Yo marina locates close by your hotel. Or if you want to opt-in for an upscale, Sala Rim Nam (Mandarin Oriental) could be a good option. Peace of mind for not dealing with Bkk traffic is priceless, believe me.
Kinlom Chomsaphan, Yok Yo and Sala Rim Nam all locate on the same side of the river with your hotel. If it's weekday night, try not to cross the river. Traffic gets worse on bridges. If you opt in for a dinner cruise as Curt mentioned, they should be able to arrange the ferry to drop you there. I can't recall my last cruise dining experience so I have no comment again.
Hope you have a good time :)