Three men have been arrested in connection with several attacks in southern Thailand since Sunday in which at least eight people died.
Insurgents staged 49 attacks on Sunday and Monday
The detained suspects were reportedly all students at Islamic schools who were drugged at the time of the attacks on a local plant known as "kratom".
The bombings, shootings and arson were the worst attacks by Islamic separatists since September.
Nearly 2,000 people have died in three years of unrest in the south.
In the latest attack on Tuesday, a 49-year old teacher was killed in a drive-by shooting in Narathiwat province, AFP news agency reported.
An army spokesman said the military could impose a curfew in the region if more large-scale attacks took place.