I'll be spending a day and night in this city. Any suggestions of things I need to see or do? Any gay areas or bars?

You won't find much in the way of Gay activity in that area (unless you happen to encounter a willing young gentleman by chance).

 

Once you've seen the ruins (you might want to see if you can find an English speaking guide, so you'll know what you're looking at), head for Bang Pa In. The roads to get there are clearly marked. You don't want to miss the Bang Pa In Palace.