The Yellow Cotton Tree (Cochlospermum regium) blooms during the winter months in Thailand. The tree is originally from South America, but is also found throughout South and Southeast Asia. There appears to be much confusion between this tree and the Silk Cotton Tree (Cochlospermum religiosum) which also has large yellow flowers. The original Cotton Tree flowers of both species are single. This double cultivar appears to be most often labeled as the Yellow Cotton Tree. The flowers are quite large and two of them placed back to back would be about the size of a softball. Wikipedia article