Chaba Kaew claim last-4 spot
The Thai women's football team will meet Myanmar in the semi-finals after beating Indonesia 5-1 in their last group match on Monday.
Thailand and Vietnam ended their group games with four points each from two matches but the Chaba Kaew were placed second in Group B because of their inferior goal difference.
Thailand and Vietnam had played to a 1-1 draw in their opening game.
Myanmar hammered Malaysia 5-0 to top Group A on Monday.
Defending champions Vietnam will face the Philippines in the other semi-final.
Both semi-final matches take place on Thursday at 7pm.
Thailand raced to a 4-0 lead in the first half against Indonesia thanks to a hat-trick from Kanyanat Chetthabutr with Silawan Intamee adding the other.
In the second half, American-Thai Suchawadee Nildhamrong, also known as Miranda Nild, scored her first goal of the tournament in the 51st minute.
Rani Mulyasari got a consolation goal for the Indonesians in the 70th minute.
"It is fortunate that we don't have any injured players for the semi-finals," Thailand coach Naruephon Kaneson said.
"We are ready for any opponent."
Thailand and Vietnam are the most successful nations in women's football at the SEA Games with each winning five titles.
Vietnam won the gold medal at the previous Games in Malaysia because of their superior goal difference following a round-robin tournament.
The Chaba Kaew also want to bounce back from their disappointing campaign at the 2019 Women's World Cup.
Several players from France 2019 are still in the team, including Suchawadee, Kanjana Sung-Ngoen, Sunisa Srangthaisong, Pitsamai Sornsai and Taneekarn Dangda.