“Glad Birthday” is a commonplace track sung at birthday events all over the world. The Spanish model of the track is “Cumpleaos Feliz.” This is the right way to sing it:
Cumpleaos feliz (Glad birthday) Te deseamos a ti (We would like you) Cumpleaos feliz (Glad birthday) Cumpleaos feliz (Glad birthday) Te deseamos a ti (We would like you)