A spike in numbers is expected on Tuesday, the final day of a 90-day amnesty for those who illegally possess marijuana for medical purposes, the Food and Drug Administration (FDA) said.
On average, 800 people a day have visited the FDA's office in Nonthaburi but that number is tipped to break 1,000 as the curtain falls, Surachoke Tangwiwat, deputy secretary-general of the FDA, said on Monday.
People who are in possession of the narcotic, or who have marijuana extracts, to treat medical ailments have until the office closes on Tuesday to register and avoid being punished, he said.
As of Monday -- when registration was suspended for the day due to it being a public holiday -- some 16,000 people had registered nationwide, he noted.
To cope with the expected spike, the office said it had prepared two more tents to give those waiting in line shelter from the scorching heat, Mr Surachoke added. This doubles the number of tents to four.
The cabinet in November approved a draft amendment to the 1979 Narcotics Act to legalise cannabis for medicinal and research purposes. However, all usage of the drug will remain strictly controlled.
Those who find it inconvenient to travel to the FDA's office or a provincial health office to register have also been allowed to do so online through the Thai Red Cross Society, he said. The Thai Red Cross will disclose the exact number later.
Meanwhile, the Department of Medical Services has unveiled the registration schedule for training courses on prescribing marijuana to patients.
Registrations began last Thursday and the training runs from June 13 to Sept 3.