The body of Seusu was found about two kilometres downstream from the river in Ban Motha village, Tambon Mae Tan in Tha Song Yang district where she was collecting oysters with 18 friends.
Initially, three Karen women reportedly drowned in the river but rescuers managed to pull out two and resuscitated them.
The 19 are students at the Kaw Tha Blay Learning Centre, which is run by Project Umbrella Burma of Dr Cynthia Maung.