The local pair successfully defeated No 1 seed Wishaya Trongcharoenchaikul and Kittiphong Wachiramanowong of Thailand 6-3, 7-6 (5) in the second round match of the doubles event.
They will next play No. 3 duo Ito Yuichi of Japan and Bowen Ouyang from China, who won 6-0, 5-6, 10-8 against Japanese Onozawa Arata and Sano Koichi.
Earlier, Thien was knocked out of the singles event, losing 3-6, 4-6 to Ito in the morning session.
Only his teammate Nam remains in the tournament on home turf, but he faces a huge challenge against No. 2 seed Dayne Kelly of Australia in the second round of the singles event today.
The tournament, which will close on September 25, has a top prize of US$10,000.