I went to Thailand with a friend for 10 days. Its a beautiful place. Best time to go is December and January. We went to area, Kanchanaburi (about 130 km northwest from Bangkok). There was a series of 7 waterfalls in which you could swim in. The water was a aqua blue but had a mystic/fogy look to it as well, even though you see through the water.
Here is an area in the waterfalls where small fish eat the dead skin from your feet! Sounds weird. It took some time to get use to. It tickles and just feels weird at first. I have read places where spas offer pedicures like this. Where you stick your feet into a large bowl of these fish. Once I was use the feeling, it felt good!