In the TV footage a bus on fire with many passengers trapped inside could be seen.
The bus was carrying Myanmar migrant workers from a Thai border town to Bangkok reportedly.
The reason for the fire that caught one of the four buses lying together to Bangkok was not immediately clear.
According to the officials, the death toll is 20, with three people injured.
The bus was carrying 47 people reportedly. It was 1:25 am when the bus caught fire in the northwestern province of Tak, near the border of Myanmar.
If the reports are true, such instances of the labourers falling victim to safety lapse are not new. It is reported that the migrant workers are paid low and they are victims of safety lapses and exploitation in Thailand.
It was only last week when at least 18 people lost their lives in a road mishap in the northeast of the country because the driver allegedly was high on drugs. Thailand has had a record of road mishaps with a large number of people losing lives in such accidents.