The ordnance was discovered by workers preparing a construction site on Monday, before being defused and removed from Nayai Chaleun village, the Ministry of National Defence was quoted as saying.
It was the fourth MK82 bomb, which has a potential blast area of 1,500 metres, to be found and removed from the district.
"There are likely to be more of these bombs in the area," said Phommachan Khammanchan, head of the clearance division of the National Regulatory Authority for UXO/Mine Action in Laos (UXO-NRA).
"We have made plans to survey UXO (unexploded ordnance) in this district in the near future and (...) clear whatever we find," he added.
The 227-kilogram MK82 was one of the most common explosive devices dropped by US forces on Laos during the Vietnam War, the ministry said.
Eighty-two other pieces of unexploded ordnance have been found in the district, including mortars, mines and grenades, according to a report by the UXO-NRA.
DPA