Nong Khai Provincial Police Commander Pol Maj-Gen Somyot Promnim led investigators to intercept a truck bearing a Bangkok registration plate while it was on Mitrapap Road, heading to Nong Khai.
At the back of the truck, police found 52 of the scaly ant-eaters, contained in 12 plastic boxes, with total weight of 267 kilogrammes.
The police detained two suspects--Rungrueng Intalang, 42, and Channarong Songsukhon, 33.
The two men told police that a village leader in Loei's Nong Hin district introduced them to a Lao national who hired them to transport a truckload pangolins from a service station in Nakhon Ratchasima for delivery to a customer in Nong Khai's Rattanawapi district.
They said this was the fourth batch of the endangered animal species that they had carried.
Pangolin scales and pangolin flesh are in high demand in Vietnam and China as medicine although their international trade is banned.
The smuggling and sale of pangolins is prohibited under the Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES.