It is believed the monkeys would have ended up in restaurants serving exotic meat.
Alerted by the Natural Resources and Environmental Crime Division (NRECD), Highway Police stopped a sedan on Highway No 2096 in Udon Thani’s Nong Mek sub-district on Tuesday.
Upon opening the boot, police found 27 sedated monkeys tied up and crammed into net bags. One of them had been suffocated to death.
The two men were handed over to Nong Han Police Station on charges of having protected animals with intent to sell.
Pol Maj-General Watcharin Phusit, NRECD commander, said his division had received a tip-off that a gang would be smuggling macaques from the Central region and South of Thailand to sell to restaurants in Laos.
The 26 rescued monkeys have been transported to the Khon Kaen wildlife sanctuary for rehabilitation before they are released into the wild.
Watcharin said the NRECD police foiled two earlier attempts to smuggle macaques into Laos this year.
On March 6, the NRECD and Highway Police arrested two suspects for trying to smuggle 47 macaques. Then on April 25, another suspect was arrested for trying to smuggle 44 macaques to Laos.