Seo is set to stand in for Chilean forward Matias Jadue, but will only be able to play in domestic competitions since he cannot be registered in time for the 2020 AFC Cup.
HCMC's both foreign forwards Jadue and Viktor Prodell suffered injuries at the club's debut at the AFC Champions League last month and are expected to need four months to recover.
Captain midfielder Do Van Thuan also suffered torn ligaments earlier.
Seo, who has moved to from K. League 1 club Busan Ipark, has in the last 10 years played for 10 different clubs in Japan and South Korea, including FC Tokyo and Ulsan Hyundai.
He played 17 times for the national U-20 team including in the 2009 U-20 World Cup.
Ho Chi Minh City FC manager Chung Hae-seong is looking for another foreign player to replace the Swedish striker Prodell before February 22, the deadline for clubs to register players for the upcoming V. League 1 season.
The V. League 1 runners-up are believed to be pursuing Vietnamese-American midfielder Lee Nguyen, who currently plays for MLS club Inter Miami.
Ho Chi Minh City has shown great ambition to challenge Hanoi FC’s dominance in domestic competitions and to go far in the AFC Cup, making many quality signings.
The club played a 2-2 draw against Myanmar’s Yangon United in their AFC Cup debut and will travel to Singapore to face Hougang United on Tuesday.