Called "ngan bun bang fai" in Thai, it is a unique festival of the Northeast, most elaborately celebrated in Yasothon province. Bamboo rockets are launched as an annual plea to gods for plenty of rainfall in the rainy season.
http://www.thaiwaysmagazine.com/thailand/thailand_festival.html
Phi Ta Khon is a tradition of the Dan Sai district of the Loei Province in Isan. It is better known as the ghost festival since it reflects the regions beliefs on ghosts and spirits. It occurs each year around June/July and is probably Thailand’s most colorful festival. Men dress up as spirits in bright colorful costumes and masks. Along with the costumes, there’s plenty of dancing and rejoicing.
http://thaholiday.com/top-5-festivals-in-thailand/
Monkey Buffet
Animals lovers would get a kick out of this bizarre festival. On the last Sunday of November each year, the town of Lopburi shows appreciation to their main tourist attraction, monkeys. They do this by serving a huge buffet of food, solely for the adorable and smart animals. This festivals makes some funny photos!
http://thaholiday.com/top-5-festivals-in-thailand/