Whats wrong with not singning the national anthem?
U know pakistan is the only country in the world which was formed in the name of Islam. However it could never embrass Islamic principals ever since its formation. On the contrary it strayed far far from Islam. See the Pakistan of today.
Coming to the point now, singing, playing, or standing in respect when the national anthem is being played is haram as per Islamic teachings. It seems that now balochi ppls have started giving some respect to Islamic principles unlike rest of country, therefore playing of national anthem abandoned at last.
Islam Question and Answer - Respect for the national anthem or flag