i thought fresh grad have no negotiation power?

short answer, no
long answer, you can try, but they will tell you no.

Wake up your idea. No bargaining power for fresh graduates basically. HR will have fixed starting salaries for different class of honors for different majors and roles.

Unless you really possess a special skillset or knowledge and this is the exact reason why they r hiring you.

have apply to join a ministry with 3+ years of private sector exp, they offer me a job.

is totally non-negotiable.

They give you $xxxx basic salary, you either say YES or NO.

haha this one not sure... maybe will ask my colleagues another day if those know lol.