Vietnam’s unseeded Thien defeated his Japanese rival 7-6 (3), 6-3 in the first set of the singles event.
He will next play the winner of the match between Ito Yuichi, another Japanese, and Jirat Navasirisomboon of Thailand in the second round.
Thiên will also pair with teammate Ly Hoang Nam in the doubles category. They will play Japan’s Ehara Hiroyasu and Onishi Ken in the first match.
In other results yesterday, Moritani Soichiro of Japan came from behind to defeat No 1 seed Hong Seong Chan of the Republic of Korea 6-7 (6), 6-4, 6-4, while Ochi Makoto won 6-2, 5-1 against Shiga Masato in an all-Japanese match.
Earlier, Ehara lost 6-7 (5), 3-6 to Wishaya Trongcharoenchaikul of Thailand.