The virtually new ATR-72 turboprop plane flying from the capital Vientiane crashed at about 4.10 p.m. (0910 GMT) just eight kilometers (five miles) short of its destination Pakse, which is near the borders of both Thailand and Cambodia.
The airline said in a statement it had yet to determine the cause of the crash, in which a senior aviation official said the tail end of Typhoon Nari may have been a factor.
Those killed were mostly Lao nationals. But seven French nationals were also killed, the country's Foreign Minister Laurent Fabius said.
South Koreans, Australians, Canadians, Taiwanese, Chinese, Burmese and Vietnamese and five Thais were also among the dead, said Thailand's foreign ministry spokesman, Sek Wannamethee.
ATR confirmed that an ATR 72-600 operated by Lao Airlines was involved in an accident today at around 4.00 pm (local time) near Pakse (Laos). The flight QV301 was operating between Vientiane and Pakse with 44 passengers and 5 crew members on board.
The aircraft, registered under RDPL-34233, was MSN (Manufacturing Serial Number) 1071, delivered from the production line in March 2013.
The ATR 72-600 is a 68-to-74-seat twin turboprop engine aircraft.