Acting on a tip-off, police at the Hua Hin railway station searched the bag of Ratthaphum Boonchuay, 25, at 8pm on Friday and found the drugs.
He was aboard the Bangkok-Sungai Kolok train.
The man, from Nakhon Si Thammarat’s Thung Song district, said he was paid Bt16,000 to take the drug from Bangkok to deliver to a recipient in Thung Song.