Deputy Prime Minister Chalerm Yubumrung said today the tablets and 60 kilograms of crystal meth were smuggled from Myanmar.
He said they were destined for sales in the capital city and nearby provinces.
The value of the drugs, hidden in dozens of pieces of luggage, was estimated at 1.5 billion baht (USD 50 million).
Police said they arrested three suspects, including a 16-year-old boy, and confiscated four pistols from them.
One of the suspects said they were hired to look after the drugs.