Singapore were not an easy encounter for Vietnam in the past, but they have not proved tough this year, losing two group stage games and drawing in the other.
Vietnam meanwhile have han an impressive run, beating Brunei 6-0, Laos 6-1 and having a remarkable come from behind victory against Indonesia last Sunday, thanks to a last minute stunner.
Singapore have been eliminated from the tournament while Vietnam are considered a candidate for the gold medal, which would be their first at SEA Games.
The Tuesday match result will decide the amount of pressure on Vietnam's last group stage match on Thursday against Thailand.