The first-leg match at Jalan Besar Stadium on Thursday remained goalless after 90 minutes. However, in the eighth minute of injury time, a mistake by goalkeeper Izwan Mahbud led to Shakir Hamzah touching the ball with his hand under pressure from Nguyen Xuan Son, resulting in a penalty.
Nguyen Tien Linh converted it in the 11th minute of added time and three minutes later, Xuan Son doubled the lead with a tap-in, sealing Vietnam's 2-0 victory.
At the post-match press conference, coach Ogura emphasized the importance of maintaining focus beyond 90 minutes and admitted that Singapore missed key chances before being punished for their mistakes.
"The punishment should have been only one goal, but unfortunately it became two," Ogura said. "It was completely the team's fault. But as I've said, the ASEAN Cup semifinals are 180 minutes long and this was just the first half."
Singapore had 67% of possession during nearly 120 minutes of the game, taking 10 shots compared to Vietnam's 11. The home side almost scored in the 68th minute when Taufik Suparno's shot was brilliantly saved by goalkeeper Nguyen Dinh Trieu.
"Vietnam were rated stronger, but we didn't back down and played good football," Ogura said. "The match was like a dramatic movie with many twists. Singapore were unlucky, but that also reflected the efforts of the team. We need to work harder."
When asked about the reasons for the loss, Ogura pointed to a lack of endurance and spirit among some players, attributing this to youth development from the U16 to the national team level.
The absence of suspended naturalized midfielder Kyoga Nakamura, who received two yellow cards in the group stage, also reduced Singapore's attacking prowess. The team struggled to sustain coordinated attacks in Vietnam's half and relied on long balls instead. Vietnam also adopted a similar style due to the challenges of playing on artificial turf.
Ogura stressed the importance of recovery, physically and mentally, ahead of the second leg at Viet Tri Stadium.
"The 0-2 result is dangerous, but anything can happen in the second leg," he said. "We lost at home despite the support of many Singaporean fans, but we can also win in front of many Vietnamese spectators."
The second leg of the semifinals is scheduled for 8 p.m. (Hanoi time) on Sunday. The ASEAN Cup semifinals do not apply the away goals rule. The team with the higher aggregate score after two legs will advance to the final.