I agree with Vulcan. A taxi to the central BKK hotels will run you about $6, maybe up to $8 to the riverside hotels. I'm not familiar with the Conrad, but BKK probably has the least expensive luxury hotels in the world, and one of the widest selections. During the low season (summer), you could get the Peninsula for $150, including breakfast.

BKK is probably the best choice if you're looking for something different than what you can get in the US. Singapore is very Westernized, a prime example of the emerging world commercial culture. I love Singapore for those aspects unique to it, but you will find Bangkok far more exotic.