Police were informed of the hit-and-run on the Bueng Kan-Phan Lan road in Ban Na Nua village at 8.30am.
The dead woman was identified as Khonma Sihalad, 77, from Muang Pakxan.
The tricycle driver, Prayoon Dichalee, 63, was severely injured and sent to the Nong Khai provincial hospital. Three other Lao women – identified as Alatae Suriwong, 26, Sanchan Suriwong, 43 and Sommai Sichan, 48 – were also injured.
The Lao women crossed the border to visit a hospital and shop at a morning market on the Thai side. They were returning to the border checkpoint when the accident happened.