Police raided a luxury home in Banglamung district and nabbed two suspects, identified as Mohammad Mehdi Manaei, 28, and Behtd Gharhyoz, 25, on Thursday.
Information they gave during police investigation led to the arrest of their companion, Ali Behnam Asadollahi, 20, later in the day.
Police seized two vehicles and 18.5kg of crystal meth (ice), reactant chemicals including methamphetamine, nail polish liquid, pseudoephedrine and ‘ice’ producing equipment.
Four days before the swoop, anti-narcotics police apprehended an Iranian with a large amount of liquid ice, which led to the major arrest of the three more suspects Thursday.
Police said Mr Asadollahi, a chemist, produced the drugs, while the others distributed them, mainly to Thai people. Raw materials were imported from abroad.
It was one of the biggest raids in Thailand, police said. They believed four other fugitives implicated in the case remain in Thailand.
Later in the day, police searched a warehouse in Nong Prue subdistrict and found 20 large air pumps and white powder in several ceramic tubes, believed to be a drug-related reactant.
The warehouse has been rented to a foreigner for nearly a year, police reported.