The division includes four natural regions and 18 provinces. Floristic affinities are close to southwestern China as well. The region is the high plateau of Thailand. Types of forests are from dry deciduous to mixed deciduous forests with large tracts of dry evergreen forests growing intermittently. Pine forests are present from above 1000 m.
Dipterocarp forests are the common feature of the region.
A significant number of bryophytes have been collected from this region. This division includes two natural regions and 10 provinces. This region is under the influence of the central and southern Indochinese flora. Dry dipterocarp forests are the main feature of the region. Savannas are also common.