For both MU and VN, your best bet is to ask at check-in. Granted you only have Elite (not Elite Plus) so YMMV, but you never know.

Whenever I fly MU I ask the check-in agent to see if they can put me further up front, and it often works especially if the flight isn't full. This doesn't work as well on regional flights, but on the long-hauls there is usually some leeway for the agent to maneuver around the seating chart and put you in a good seat.

For VN, I didn't even need to ask: when I flew HKG-SGN and back I was offered better seating at check-in and I said yes on both legs.