Thai authorities have foiled two attempts to smuggle in a total of one tonne of ketum leaves from Malaysia with the arrest of four local men.

In the first case, a source said a team of police and military personnel had stopped a suspicious-looking sampan), carrying two men, in Satun waters about 6pm today.

"Upon realising the authorities' presence, the two men had thrown away packages containing the leaves into the sea and tried to flee the scene. However, they failed to escape," the source said.

According to the source, the suspects, aged 22 and 42, from the Langgu district of Satun near Kedah, Malaysia, admitted that this was their fourth arrest for smuggling ketum leaves.

Meanwhile, in another case, the authorities detained two men travelling in two four-wheel drive vehicles after the discovery of 890kg of the leaves which had just been smuggled in from Malaysia.

Both of the suspects confessed that the ketum leaves were meant to be sold on the holiday island of Phuket, another police source said.

-- BERNAMA