He threatened to detonate a bomb, which he left behind after escaping on a motorbike.
Police in Dong Nai Province are looking for a man who robbed a bank on Friday.
Staff at the bank said he placed what looked like a bomb on the counter and told them to empty the tills. VND25 million ($1,100) was taken during the heist. More than 20 people were in the office at the time.
Police and military officers are investigating the case.
Bank robberies are rare in Vietnam and each case usually involves a single individual and small amount of cash.
In May, police in the southern province of Tra Vinh arrested a 29-year-old man a month after he allegedly used a gun to rob more than VND2 billion ($88,000) from a Vietcombank branch.