Just a short note before I went to bed :)
Songkran is probably the best times to *stay* in Bangkok. Yeap, you heard it right. And why is that you ask? Because many people will return to their hometown to see their families. The results is reduced traffic (also because it is long holiday), reduced people, and in general less crowded city.
So if you ever think of visiting Bangkok, Songkran is the best times. Sure some places might be close, you will get wet along the way but you will get where you wants to go a lot faster than usual :)