Definitely can reach there by 7am. I think you can reach there
around 0630 - 0645.
If you are living near Bedok MRT, you can take MRT from Bedok to
AMK. Probably reach AMK by 0611 earliest. After that you can take
169 from AMK. The earliest bus for 169 is around 0530, so no issues
for that.
Alternatively, you can take 25 from Bedok to AMK. Bus 25 starts
operating from 0515 onwards during weekdays and will reach AMK
around 0555 - 0605.
After that, you can take 169 from there.