Top seed Le Quang Liem slipped to third spot in Group A after drawing his ninth round match against Ray Robson of the US at the SPICE Cup in Texas on Monday (local time).
The 25th-ranked Liem beat Robson in the first leg but the American used the advantage of playing with white pieces to fight to a draw after 82 moves in four hours.
The second consecutive draw and the fourth draw at the tournament had Liem in third place behind the 100th-ranked German Georg Meier, who beat Yury Shulman of the US. Meier has the same 14 points as Liem but his additional figures are greater.
Group leader Leinier Dominguez Perez of Cuba, ranked 38th in the world, could only raise his points from 14 to 15 after being held by the 77th-ranked French rival Sebastien Feller.
Feller and Robon are in the fourth and fifth positions with eight points each while Yury Shulman is at the bottom with seven points.
Liem can win the championship if he can beat Perez in the final round on Tuesday local time (Wednesday morning in Vietnam). In the event Meier also wins his final round match, the championship will be decided on their additional figures.
Liem, the only Vietnamese to enter the world top 100, will have the advantage of playing with white pieces in the decisive match against the Cuban.