About one in 10 of the 20,000 people who registered as being in the illegal possession of cannabis to treat medical ailments were found to have diseases that justified the use of the narcotic, the Food and Drug Administration (FDA) announced on Tuesday.
Most of the 2,000 eligible registrants have cancer, while 50 suffer from diseases that destroy nerve tissue, or have neuralgia, epilepsy or are experiencing negative side effects from chemotherapy, according to Dr Surachoke Tangwiwat, the FDA's deputy chief.
The FDA will give priority to those 2,000 people when dispensing marijuana, which has recently been approved as legal for medical use under certain circumstances.
"They will be the top priority. The FDA will continue to acquire and supply them with cannabis extract oil via local hospitals," said Dr Surachoke.
The FDA ended its 90-day amnesty on Tuesday, during which time individuals and medical practitioners who came forward to register as having a legitimate need to justify their use of the drug would not be punished. The programme was launched on Feb 27.
Marijuana has been classified as a narcotic in Thailand since 1979, with possessing it a criminal offence.
The amnesty followed a change to the narcotics law in December legalising use of the drug for medical purposes only.
Dr Surachoke said most of the people who had registered over the past three months suffered from diseases or ailments that did not necessary support the use of cannabis as a form of treatment. Many were young people, he added.
Common among the diseases presented were migraines, diabetes and heart disease, according to the FDA.
"We are concerned that more people are experiencing side-effects due to the unnecessary use of cannabis. Today we can see that most of the people who have come to us to register are quite young. Most of them claimed to have symptoms like headaches and an inability to sleep, for which there are better curatives," he said.
Among those who registered on the final day was a 24-year-old student who gave his name as Song.
Song reported that he was in possession of 200 grammes of cannabis, which he said he had been taking for the past five months to help him cope with the two aforementioned problems, migraines and insomnia.
"From now on, I need to ask a doctor to prescribe cannabis oil," Song told the Bangkok Post, adding he hoped to receive the drug free of charge.
Hundreds of people rushed to register on the last day, with 150 doing so at the Ministry of Public Health's offices in Phitsanulok province alone.
In a related development, a pro-cannabis legalisation group embarked on a 265-kilometre walkathon on Tuesday from Phichit to Suphan Buri.
Dubbed "Cannabis Walk Thailand", it is being spearheaded by Daycha Siripatra, who earlier launched the Khaokwan Foundation and is a researcher on cannabis for medical treatment.