What does semoga bahagia means?

The answer is:

May You Achieve Happiness

For extra info,this is the rest of the song:

Together we progress onward Clever at seeking knowledge Take care of your health And be courteous to your friends With a heart that is clean and pure Together we respect and do good Watch your behaviour, oh youths Customs and cultures, hold them high Quickly reach your ambitions, oh youths So that we'll have our worth, in the eyes of the world If we are lazy and forgetful Our lives are for nothing A good soul, a healthy and fresh mind Hard work and patience, definitely brings happiness Soft-spoken is the lady Energetic and tenacious is the man Charitable, always contributing Protecting and giving service

Attain a respectable position, oh youths Be hardworking so that you will succeed, may you achieve happiness