The two teams showed off their superior level compared to the others, before their final group stage match today at the Bishan Stadium.
The match will be aired live on VTV6 channel from 7.30pm, Hanoi time.
Vietnam are on the top of Group B, with 12 points from four matches. Thailand come second with the same points but less goal difference.
Although both have secured the tickets to the semi-finals, they still want to beat their traditional archrival to emerge as the group leader as that will allow them to play in a later match in the semis.
And to many fans of both sides, the match is an early final of the tournament.
However, coaches have their own plans.
In Toshyia Miura's Vietnam squad, seven players have received yellow cards. If they get one more in today's match, they will be sidelined in the important semi-final game.
Miura who made four different starting squads in previous matches can rest his key players to avoid injuries and cards.
It will not be surprising if the Japanese makes another team, as he said last week, "We need to rotate our players. We have little choice as we have to play six matches in 14 days."
"And, even though we play games more than teams in Group A, we are still only allowed to register the same number of 18 players. So, we have to make rotations, otherwise they will not last the pace."
Under his rotation, 19 of 20 players were on the field, and only goalie Phi Minh Long played all games. His plan helped to keep all players in good shape for their next match and five strikers had chances to work with each other and all of them scored as well. The team has grabbed 16 goals as of now.
Asked about playmaker Nguyen Cong Phuong's absence from the match versus East Timor, Miura said: "With the major match against Thailand coming up, we want to make sure that everyone gets enough rest.
"We are playing so many matches within a short space and with limited number of players. It is for this reason that we want Cong Phuong to be fresh for the final game in the group."
On June 9, Miura asked for a closed door training for Vietnam on their last day before the game. Media will get only 15 minutes prior to their training shift.
While the Thais must win to lead the group, Vietnam will only have to grab a draw.
Thailand might have to considered their contingent too as they have six players with yellow cards.
Assistant coach Promrut Choketawee in a talk with reporters said he could use a second team for the game.
Chanathip and Sarach will be rested for their safety. Nurul, Narubadin, and Tanaboon will be on the bench to save their best for the semi-finals. Pinyo Inpinit, Tristian Somchai Do, and Siwakorn Chakkuprasat will watch their teammates playing as they received one card.
However, leading scorer with four goals, Chananan Pombubpha, will start with left defender Peerapat Notechaiya who has recovered from his injury.
All of their players have been asked to stay in their hotel and must ask the team's doctors about any food and drink that they have.
In 20 years, Vietnam have played Thailand nine times in the SEA Games. Thailand won six and drew three.
Of the six losses to Thailand, four were finals.
In their latest meets, Thailand met Vietnam twice and walked away with a win.
The first was a friendly in March, in which Vietnam lost 1-3, in Bangkok. Thailand beat Vietnam 1-0 in a World Cup qualifier last month.