Police, commandos, and corrections officials are guarding a throng of security buses going in a convoy to Khao Bin Prison in the western province of Ratchaburi.
Bang Kwang Prison houses 4,567 prisoners serving jail terms of 10 years to life imprisonment as well as for capital punishment.
Corrections Department director-general Suchart Wongananthachai said he ordered the tranfer of the first group of Bang Kwang inmates as the flood is looming large. The remaining prisoners will be moved to other prisons in due course.
Prisoners in several prisons in flood-prone areas would also be moved to areas not affected by flood, the senior official said.