The tablets had been in large sacks at the back of a six-wheeled truck that was intercepted by Thai police officers and soldiers on Tuesday at a security checkpoint in western Kanchanaburi province, police said.
A man and a woman who were in the truck have been arrested, they added.
In terms of Asia meth drug busts, the seizure was second only to one of more than 55 million meth tablets in Laos near the Golden Triangle region, according to Jeremy Douglas, Southeast Asia regional representative for the United Nations Office on Drugs and Crime.
Asian crime syndicates work with ethnic armed militias to smuggle methamphetamine produced in Myanmar's northern Shan state southwards, Douglas said, adding that distribution networks reached as far as Japan and New Zealand.
"Production is expanding, they've worked together before, and there is money to be made," he told Reuters.
Douglas said seizures by authorities were having only a minimal impact on the flow of illicit drugs in the region as organised crime groups were increasing supply and lowering the cost of methamphetamine.
Unrest in Myanmar since a 2021 coup has also allowed smugglers to expand their routes and operations, he said.
(Reporting by Panu Wongcha-um; Editing by Edwina Gibbs)
