Dr Suwannachai Wattanayingcharoenchai, director-general of the Disease Control Department, said the ministry was monitoring all at-risk persons in every province to curb the spread of the contagion.
The at-risk group includes medical personnel, delivery persons, public transport officials, jail officials, inmates, postmen, migrant workers and those who work in public venues.
These people will be tested randomly using a pool sample method and Reverse Transcription PCR (RT-PCR) will be used to examine phlegm samples.
About 100,000 people are expected to be screened and 80 per cent have passed the test. Though some showed genetic materials of Covid-19, they were recovered patients and cannot spread the virus.
Suwannachai said the at-risk group should all be tested within June adding that the three factors that helped control the spread of Covid-19 were keeping imports of the virus low, hunting down the infected and increasing hygiene discipline among people.
However, just screening cannot confirm that Thailand is free from Covid-19, because asymptomatic people are still around so preventive measures are still required.
After the fourth round of lifting measures, Thais may have gone back to life as usual, but they must continue wearing face masks, cleaning hands and observing social-distancing measures in order to end the disease in Thailand.