Hi Dermot,
You don't have much time there. i would say that one of the must see's in BK is the grand palace. i know you can do it on your own but I would take a tour. apart from that it would be an idea to get on a boat down the river and just marvel at what is life in BK.
You may find that you are really tired and need to aclimatise a bit.
Where are you staying?
shopping mBK worth a look and Emporium only if you want to look at the real stuff at 100's of squids for a handbag.
I think that the shopping and grand palace would be enough.

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Kiss
God laughs at people who make plans.