Vũ Hà Minh Đức of Việt Nam came second at the International Tennis Federation World Tour Junior, J5 Phnom Penh, on Saturday.
An is seeking his second berth at the world's biggest sporting event, which will be held this summer in Tokyo.
Việt Nam badminton legend Nguyễn Tiến Minh is targeting a spot at the Tokyo Olympics, hoping to make it his fourth appearance at the games.
Lý Hoàng Nam won the historic tennis gold medal for Việt Nam at the SEA Games on Friday morning in the Philippines.
Việt Nam have jumped two steps to No 92 in FIFA's November world ranking.
Both Việt Nam coach Park Hang-seo and his counterpart Tan Cheng Hoe trained behind closed doors before the game, their first since the 2018 AFF Cup final last December.