What are the beliefs behind Wai Kru Ceremony?

In my opinion, Wai Kru Ceremony is not only the day that the students pay respect to their teachers but also means the belief of Thai culture and Buddhism that Thai students express gratitude to their teachers. This belief will bring them the successful future. For example, the symbolic of the flowers that they use for this ceremony. All of them have the good meaning. However, Wai Kru ceremony also has for most of history as a folk tradition passed on from generation to generation throughout every year.