What are the beliefs behind Wai Kru Ceremony?

In my opinion Wai Kru Ceremony is the important ceremony in Thailand.

The students will thank you their teachers that teach them .We believe teacher is a second mom because teacher teaches and gives us a knowledge. Sometimes we do something wrong teacher will advise us to be a good person in the future .But sometimes in my opinion it is difficult to arrange the ceremony .In the ceremony firstly, the students are singing Wai Kru song ,In the music it will talk about teachers that teach students and tell students to be a good person .Second, the representatives of student will give flower pan to teacher for thank you to teacher. Finally, agent student will tell something to teachers.