The pattern of drug use in Thailand remained relatively unchanged between 2004 and 2007 with methamphetamine in pill form, locally known as yama or yaba, ranking as the most commonly used drug, followed by cannabis and crystalline methamphetamine. However, in 2008 Thai authorities reported a change in pattern, with cannabis becoming the most commonly used drug, followed by kratom, methamphetamine pills and inhalants.

Crystalline methamphetamine dropped considerably from being ranked number three in 2007 to number eight in 2008, although the trend in use was reported as being on the increase. Heroin and ecstasy were ranked sixth and seventh respectively in 2008 and use was reported to be on the decline. The rank for opium, although reported as having a stable trend in both 2007 and 2008, increased to five in 2008 from nine in the previous year.

A noticeable change occurred in 2007 with the first reported increase in methamphetamine use in pill form after a four year decline following the war on drugs in 2003. The increasing trend was sustained in 2008. Crystalline methamphetamine showed an increasing use trend in each year of the 2003-2008 period, with the exception of 2007, when a decline was reported.

Heroin use has shown a declining trend in all but one year since 2003, while cannabis and kratom appear to have become increasingly popular, possibly due to concerted law enforcement efforts against methamphetamine and other drugs.

In terms of route of administration, use of methamphetamine in pill form saw a shift from oral ingestion to smoking, and most recently also to injection, routes increasingly associated with greater drug availability and health-related risks. It has been suggested that the shift from ingestion to smoking indicated a shift in motivation for use from bolstering endurance during manual labour to recreational use (Liewtiwong, 1996).