Hoai finished the 150km race from Hanoi to Thanh Hoa Province with a timing of 3 hours, 22 minutes and 48 seconds.
Le Nguyet Minh, who got married early this month, was second. The cyclist of the VUS-HCM City team crossed the finish line just a hair gap after the winner.
Le Ngoc Son of Gao Hat Ngoc Troi An Giang was third.
The first stage of 50 laps around Hoan Kiem Lake was won by Nguyen Cuong Khang of the HCM City Youth squad.
After two stages, Khang maintained his lead in the tour with a total timing of 4:33.24s.
He was followed by teammate Nguyen Minh Viet and Minh.
An Giang Plant Protection took the top position in the team ranking. HCM City Youth crew came second and Bike Life Dong Nai were third.
The third stage will see the riders tour the 187km from Thanh Hoa to HaTinh Province on July 17.