In Thailand most workers do not receive the generous holiday/vacation leave allowances people do in the west, although this is offset by the greater number of public holidays Thais enjoy. Many public holidays are based around festivals. Clearly, Thai people want to make the most of these holidays by taking a break or visiting relatives at home in a different province. They are very often periods of significant increase in domestic tourism and travel. During some of the Thai public holidays, you might find hotels and resorts fully booked and it might not be possible to get transportation to the places you want to visit. Clearly a bit of planning is in order.
The festivals that often take place during public holidays are great times to see aspects of 'real' Thailand and to feel more involved than you usually might. This is especially true of the Songkran festival. They can though be periods of frustration if travel plans do not go right. Reserve hotels and buy tickets at least a few weeks in advance. In addition, avoid the hassles getting back to Bangkok on the last day a holiday by staying a couple of extra days out of town.