A Lao Airlines plane carrying more than 40 people, including French and Thai citizens, from the capital Vientiane to the southern town of Pakse crashed killing all on board on Wednesday.
Thai television showed a photograph of the ATR 72 turboprop plane partly submerged in shallow water on a stretch of the Mekong, the tail severed. Another television channel showed what appeared to be several bodies on the bank of the river.
Remnants of Typhoon Nari have been hitting the area. Pakse has received more than 3.9 inches of rain since Tuesday. At least seven French nationals were among the dead, French Foreign Minister Laurent Fabius said in a prepared statement released Wednesday.
Lao Airlines is the national carrier of the communist state and has operated since 1976. Its aircraft carried 658,000 passengers last year and it has a fleet of just 14 planes, mostly propeller-driven.
It operates on seven domestic routes and has international flights to China, Cambodia, Thailand, Vietnam and Singapore.