The Department of Land Transport (DLT) will be asking drivers seeking new and renewed driving licences to provide a medical certificate from next Friday.
"As drivers' physical fitness possibly changes with increasing age and they might also develop chronic diseases, the ministry needs the certificate to ensure it won't affect their driving ability," DLT director-general Chirute Visalachitra said on Friday.
The certificate, he said, needed to comply with standards set by the Medical Council of Thailand (MCT).
It must come in two parts, the first being a statement from the driver confirming his/her fitness to drive and the second being an appraisal by doctors.
Applicants will then be required to undergo tests at Land Transport offices nationwide for colour blindness, eyesight and reaction time.
Until now, motorists have not needed to present medical certificates when applying for new or renewed drivers' licences, a loophole that is regarded as having compromised road safety.
About one million licences valid for life were issued to drivers of cars and motorcycles before 2003 when the government decided a driver's licence should only be valid for a maximum of five years.