Thailand deployed about 10,000 soldiers on Friday to help victims of floods that have killed 188 people and left vast swathes of the country under water.

Backed by 500 military vehicles and more than 100 boats equipped with loud speakers and flashlights, the troops will patrol flood-stricken areas to ensure people's safety, the army chief said.

"The military is ready to ease the plight of the people so please support the soldiers," General Prayut Chan-O-Cha told reporters before leaving Bangkok to inspect one of the 23 waterlogged provinces.

He said that army had also dispatched 12 medical teams to offer first-aid and psychological treatment.

The deployment came after Prime Minister Yingluck Shinawatra, whose older brother Thaksin was ousted from office by royalist generals in 2006, ordered the military to take action to assist flood victims.

She also instructed her cabinet ministers to stay overnight in flood-hit provinces to gather first-hand information about the situation.

The floods have damaged the homes or livelihoods of 1.9 million Thais, according to the Department of Disaster Prevention and Mitigation.

The northern city of Chiang Mai, a popular tourist destination, has been inundated and the authorities are battling to stop the floods reaching central Bangkok.