tkoose
For a DEC onto the B747 it was a requirement that you had to have at least 2000 hrs wide-body command in your log book out of a total of about 3000 hours command and 5000 TT.
I'm not up to date on SIA current policy so the best way for you to find out is to apply for B747 and see what they offer you, you may get B777. In your shoes I think I would invest in a telephone call and ask them outright what they would consider you for. Best of luck.