The clash occurred yesterday in a mountainous border area in the Mae Sai district of northernmost Chiang Rai province -- part of the Golden Triangle region.
"Six bodies were found at clash site along with seven bags of methamphetamines," Colonel Nattawut Yuwan, commander of the Mae Sai police, told AFP by telephone.
"We suspect they were hilltribe (Muser) people," he said, adding the suspects had been travelling by foot and the clash happened quite close to the border with Myanmar.
Clashes between police and drug traffickers are fairly common in Thailand's remote border regions.