Ray, I recommend you do the Hall of Opium. It's housed in an impressive building right along the roadside. We did it almost two years ago and found it a very rewarding experience. We went there on a weekday morning and were almost the only visitors.
Not only is it highly informative, but it's beautifully made, too. I'm sure you will enjoy it!
Oh, are you aware that the Chiang Saen bike week will take place on 28/29NOV? We will be there, why don't you include this event in your planning? Perhaps we can abuse some innocent beers together :wink