In this post I’ll try and offer a superficial explanation for the use of water and powder during the Songkran festival. Detailed explanations of the festival’s origins can easily be found with a few google searches, but my focus is on how the tradition evolved to what we see today. This is based partly on some Internet research, combined with what I’ve gotten from the boys.

Songkran apparently originates in northern Thailand, Laos and Cambodia, and over time has found its way into other regions of Thailand. I mention this, because there are some variations on how Songkran is celebrated from one region to the other. There are also differences in how things are done in rural areas compared to the big cities. Like many things in Thailand, the explanation you get for something is often influenced by the regional practices of the individual providing the answer. In addition, the younger generations my not have a complete understanding of the more traditional roots of some things. Thus, it can be difficult to get one simple answer for something like why is powder used. Factor in limited English skills and the quest for solid answers can be a bit challenging, to say the least.
WATER
The craziness of dumping water on each other originates from a formal ceremony, which still exists today, that pays respect to elders. I’ll skip over the details, but the water part is limited to poring a small cup of scented water on an elder’s hands. Some boys tell me it’s also pored on feet.  This later evolved into the tradition of poring a small cup of water on the shoulders of friends and passers by, which is still practiced today, even in Bangkok.
At some point it was decided that after the formal ceremony with elders the younger boys and girls could have fun splashing each other with water. This is significant, because it was the only time of the year opposite sexes were allowed to mix and touch each other without fear of retribution. More about this when we get to the origins of smearing powder on each other.
Today, boys will tell you that the splashing of water is symbolic of cleansing each other, so everyone will be fresh for the New Year. If you think the water fights are crazy in Thailand, try Cambodia where it’s common practice to throw plastic bags of water at moving vehicles, motorcycles included!
POWDER
While it has evolved somewhat, this is one of the oldest Songkran traditions. Originally the white paste was a sign of protection and promised to ward off evil. The person with the paste was often older and he or she applied it to various parts of the face, neck and torso of others. One was expected to leave this paste on until it washes off. At least in some regions, dry powder was also used. One boy told me the traditional dry powder is very expensive and impractical for the celebrations we see today. Even so, it is still common to have dry baby powder placed on you cheeks and/or forehead, even a few days before the actual festival begins. I’ve had it done to me by the check out clerk at the local grocery store.
I asked three boys about the use of powder, all in the same room at the same time, and each from a different region of Thailand - Central, Isan and South. Two had moderate English skills and one was quite proficient. The first answer I got was the always popular, “for good luck.” This was followed by, “for fun.” But after considerable digging I learned something very interesting.
Earlier I mentioned that in the past youth were allowed to have water fights, and this was the only time of the year opposite sexes were permitted to mix and touch each other so liberally. Well, the boys told me this custom of smearing powder paste on a stranger’s cheeks is a way to touch someone you find attractive, without fear of retribution. While this is generally considered something the opposite sexes take advantage of, these three gay boys said the same holds true for them touching other boys. From what I gather, this liberty is typically limited to the touching of another individual’s cheeks and possibly forehead. The more aggressive covering of an individual with powder is largely restricted to friends or a stranger that has gotten particularly aggressive in his or her festive spirit. In other words, it’s just for fun.
CONDUCT
I’m sure everyone has there own experiences, but I’ve found as long as you don’t engage, and are not in a location where a large group is having a water fight, the participants will usually leave a westerner, or older Thai, alone as he or she passes by. In all the years I’ve lived here not once has anyone gotten me wet at the neighborhood street-side gatherings of a few Thais with hose and tub of water. The only time I’ve ever gotten wet was from a couple of children that politely pored a small cup of water on my shoulder and wished me a happy new year.
I’m not suggesting one is totally immune from the occasional soaking, but as a general rule the stories you hear about having to stay indoors for three days are grossly exaggerated. At least that’s been my experience in BKK. Pattaya may very well be a different story. Regardless, I don’t advise venturing out without cell phone, wallet and other valuables safely sealed in plastic bags.