Hi Doan
I got PR request after seeing this line within 1-2 days. I think you should contact Singapore some how (email or phone) to ask about status. I know one case that got refused because of waiting too long. Singapore sent letter to request PP, but the wife never receive it (lost) after waiting 3 months, the husband in Canada got a refused letter reason: they did not hand in PP on time.
In the PPR, they clearly said you need to hand in your PP within 60days after receiving this letter.
Goodluck.