When we visited Phuket we saw how cost effective it was to book tours from the travel agents at the markets. I manged to save quite a bit by asking them to write down their best price (often around 50% off the brochure price) and then booked with the best deal.
Does a similar approach work in Bangkok? We want to do the Bridge over River Kwai tour with the bamboo rafting and elephant ride. The best price I've seen online is 2000 Baht per person. Just wondering if I should book this now online, or wait til we get to the markets and see what's on offer?