According to a Thai police officer, investigations are under progress and between 60 and 70 per cent completed.
"The suspects can face the death penalty following the large seizure of methamphetamine ('ice') and heroin from them. The police, on their part, have obtained strong evidence against them.
"However, despite the possibility of facing the maximum sentence of death under the stipulated charge, Thai courts seldom hand down the death penalty and prefer the long-term jail sentence, instead," he told Bernama on Sunday.
On March 23 and 24, the Malaysians, in two groups of 15 and six men were arrested by Thai Railway police at four different train stations and in a passenger van.
Seized from them were 226kg of methamphetamine and 8kg of heroin kept in backpacks.
The train they were travelling in was enroute to Butterworth from Hualamphong, Bangkok.
Thai police have described the drug haul as one of the largest confiscated in recent times, which could fetch about RM400mil in Europe.
The Thai police officer also divulged that based on information obtained, there was a link between the Malaysian suspects and a major drug trafficker whose nationality he declined to divulge.
In an interview with Bernama previously, Police Col Puttidej Bunkrapue from the Thai Railway Police said investigations revealed the drug smuggling attempt by the 21 Malaysian suspects was masterminded by three men.
The 21 Malaysians are currently under remand at Bangkok's Central Correctional Institution for Drug Addicts. - Bernama