Bus driver Kuanchit (last name withheld) said he noticed smoke pouring from the luggage compartment at around 8am, soon after picking up a Polish tour group from Bangkok Palace Hotel.
The bus had entered an elevated section of the Si Rat Expressway in Chatuchak district when it caught fire. The driver stopped the vehicle immediately in the left-hand-side lane and evacuated all the passengers to safety.
Firefighters arrived at the scene to find the bus ablaze on the highway above Bangkok’s main rail hub, Krung Thep Aphiwat Central Terminal.
Long traffic jams built up on the expressway as emergency services dealt with the incident.
Firefighters took around 20 minutes to extinguish the flames but the bus was completely gutted by the blaze. Passengers also lost luggage in the inferno.
Officials towed the burnt-out wreck away at 9.38am, and traffic flow quickly returned to normal.
Expressway Police Station 2 superintendent Colonel Parin Chanlert confirmed the fire had been doused and the traffic jams were easing.
Thai actress Pornchita "Benz" na Songkhla posted a clip of the incident online, commenting that the expressway fire was frightening. She hoped that no one had been injured in the incident.