It was Saturday morning local time when the residential building, which was located in a luxury area in western Bangkok, started burning.
The property burned for about an hour before the flames could be extinguished.
Shortly afterwards, when firefighters and rescue workers went through the remains of the three-story building, it collapsed.
- The cause of the collapse is unknown.
The fire may be the reason why the interior of the property collapsed, says rescue leader Jiratthikorn Banjongkit.
Four of the dead are said to be rescue workers and one of the dead was living in the house.
More may have been buried
There are fears that more people will be buried under fallen concrete walls and other landslides.
Exactly how rescue workers will be able to reach them is currently unclear, according to Bangkok Governor Aswin Kwanmuang.
"We must gradually drill and use small tools because larger equipment risks causing further collapses," said the governor.
What caused the fire is being investigated.
One of the rescue workers captured the house collapse on film. Watch the clip in the player.