The small long-tailed boat with four adults and six children onboard sunk when it was crossing from the Myanmar side to the Thai side in Ban Lortha in Tha Song Yang district.
Official said the Myanmar boat driver, a two girls and a boy had disappeared in the swollen river.
One of the girls was a Thai identified as Navapornprai Boonsil, 11, a resident of Ban Mae Wei Tha village in Tambon Tha Song Yang.