Binh was just finalising the banking when the robber threatened him with a big, long-handled knife, demanding cash.
"He locked the door between the bar and the restaurant so no one could get in," Binh said.
When the robber had the cash and left through the back door, Binh chased him, yelling in English and Vietnamese.
"It was all over in about four-and-a-half minutes and I can't sleep because he's still out there," he said.
The man is described as 1.65m tall, of slim build, wearing a light-blue rain jacket and blue jeans. He had a dark-coloured piece of material wrapped round his head and neck, and was carrying the dark backpack.
It was the third aggravated robbery in town in six weeks, along with a ram raid at BP Connect, and business owners and Binh are worried.
"It's very hard to prevent these without a community-driven solution and the help of our district council," Binh said.
"It's been a traumatic shock, but I don't see a solution unless it's driven by our community. This is a very tough period and we want the police to find the culprit, because we're very insecure and business people are worried."
A lack of lighting and CCTV cameras along the back alley behind the Saigon premises and the New World car park needs to be addressed, Binh said.
Under-veranda lighting isn't working on the Barraud St side of the building either.
"Facing this is enough to wake me up at night," Binh said.
It was the second robbery at the Saigon in six months, but this time it's different, the manager said.
"We've improved security and last time someone entered the premises at 3am, breaking a window as they did so."
This is another in a number of aggravated robberies in Dannevirke recently including Caltex Westlow service station, Dannevirke Four Square and a ram raid at BP Connect on May 1, all targeting cigarettes and cash.
And in late March thieves caused thousands of dollars worth of damage to DJ's Dairy, in Woodville, when they tried to steal the cigarette cabinet, breaking windows in the process. The dairy's till, Lotto machine and pie warmer were also broken in the raid.
Acting Sergeant Gary McKernon told the Dannevirke News there is CCTV security camera footage from the Saigon robbery, with police forensics team and Dannevirke CIB investigating.
And with retailers feeling uneasy, McKernon said police will be visiting all likely targets in Dannevirke to discuss crime prevention.
"We're about to receive a crime prevention app from Counties Manukau Police which has a yes/no answer questionnaire which can help business owners assess their vulnerability," he said.
Suresh Patel of Shires Fruit and Vege Market said business owners in Dannevirke are feeling "quite uneasy".
"Obviously it's a scary thought when people can come into your premises armed with a knife," he said.
"It can happen at any time."
Patel, who has been offering support to staff at Saigon, said he thought McKernon's approach to retailers was a good idea, but shop owners need to be more vigilant too.
"They need to keep reviewing their systems and safety policies and bear in mind safety is the first priority," he said.
"It's better to be over-prepared and if anyone has a security system or monitoring equipment they need to be looking at how effective they are. If they're not, they should be updating them to make them more effective."
Two teenagers, 17 and 16 years old, have been charged with aggravated robbery after entering Caltex Westlow in late March and allegedly pulling a pistol before demanding cash and cigarettes.
Anyone with information about recent robberies can call Dannevirke police on (06) 374 4500 or Crimestoppers on 0800 555 111.
