Acting on a tip-off, police arrested Hemmarat Chuchian, 38, at his house in Moo 1 in Tambon Na Thom in Muang district at 4.30pm.
Police found two litres of kratom-boiled water, 400 grams of kratom leaves, 204 methamphetamine pills, and 35.49 grams of crystal meth at his house.
Police also seized a 9mm pistol, 18 rounds of 9mm ammunition and Bt400,000 in cash.
Hemmarat said he bought the drug from Santiparp Ketchu to resell. Santiparp was arrested later in the evening at his house in Moo 2 village in the same tambon.
Police seized 62 meth pills and 0.69 grams of crystal meth.