The Boston Licensing Board this week will decide whether to revoke Pho So 1's liquor license - or possibly even shut the restaurant completely - because police keep finding it open and serving beer way after its licensed 10 p.m. closing time.

The board held a hearing Tuesday morning on the restaurant's fifth after-hours violation in seven months. With the aid of an interpreter, owner Huy Nguyen said he gets it this time - and recently installed a large sign warning patrons they have to be out by 10 p.m.

But board Chairwoman Christine Pulgini said Nguyen claimed to have gotten it at past hearings, as well, and asked Nguyen if he keeps staying open late because of "an inability to conduct your licensed premise within the law" or because of "an unwillingness" to do so.

One regular patron, Henry Wessmann, who said he has dinner at Pho So 1 at least once a week, pleaded for mercy.

He said board members and other non-Vietnamese people just can't understand the tightness of Vietnamese culture and said that's caused the clash with city of Boston licensing requirements. As an example, he said one of the earlier violations was for a birthday party that went late.

And the things Nguyen has gone through as a refugee, well, those are "things we don't understand," Wessmann said.

Wessmann, a lifelong Dorchester resident, said Nguyen is a hard worker who has helped revive Fields Corner from its "pretty seedy" past.

Now, he said, Nguyen "gets it - he's scared [of losing his business]."

"We were given that reassurance the second time," when Nguyen's son testified for him, Pulgini answered.

BPD Sgt. Det. Robert Mulvoy said he and his partner were driving in the area of Adams Street and Dorchester Avenue shortly before midnight on Feb. 8, when they noticed the lights and TV still on at Pho So 1. They stopped to investigate and found three patrons inside, at least two with full bottles of beer.

When they reminded Nguyen of his legal closing time and asked him to escort the patrons out, he refused, Mulvey said, adding one of the patrons began swearing and yelling at the officers.

After his testimony, Pulgini asked Nguyen for his side. When he started talking about 1975, though, Pulgini cut him off and asked for an explanation of the specific incident. Before he could answer, though, Mulvey showed him a picture of the alleged swearing guy, whom he said was involved in past after-hours yelling and swearing as well.

Nguyen said that the man was his brother and that it was Mulvey who started the argument with him - which Mulvey denied.

"He's trying to obey the law [now]," his interpreter said. Pulgini answered, "I've heard that before. This isn't an isolated issue."

At a meeting Thursday, the board could revoke Pho So 1's liquor license, which would let it continue to serve food, revoke the food-serving license as well or order the restaurant shut for several days as punishment.