8 January 2017 Last updated at 13:54 GMT
It's been reported that at least 12 people have died.
In some parts of the country so much rain has fallen that the water has reached house roofs and roads have been turned into rivers.
The government say the army is helping to evacuate flood victims, provide temporary shelter and give out emergency aid.
The rain isn't expected to stop for at least two more days, according to Thailand's weather department, who warn more flash floods may be on the way.
Record rainfall in Thailand, in south-east Asia, has caused flooding and devastation.