Ekwegbalu James Nzube, 45, said he got acquainted with another Nigerian, Jone, in China in 2014, and the latter had hired him to transport drugs from Cambodia to Vietnam.
In March he came to Ho Chi Minh City before going to Cambodia to fetch the drugs for which he was paid $2,000.
But while illegally crossing the border into Vietnam last July he was caught by border guards in Tay Ninh Province.
In his rucksack they found four plastic bags with nearly four kg of meth.
Vietnam has some of the world’s toughest drug laws. Those convicted of possessing or smuggling more than 600 g of heroin or over 2.5 kg of methamphetamine face death.