The Thai government has unveiled plans to upgrade four regional airports in the coming years.

The Bangkok Post reports that the country’s Department of Airports will invest almost THB24 billion (US$682 million) on the redevelopment of the airports in Krabi, Trang and Nakhon Si Thammarat in southern Thailand, and Khon Kaen airport in the northeast of the country.

Under the plan, Krabi International Airport’s existing capacity of four million passengers per year will be increased, in line with an expected doubling of traffic over the coming years, while Nakhon Si Thammarat’s capacity will be boosted from 1.1m to 3-4m passengers per year.

No information was provided about Trang Airport, and Khon Kaen’s existing annual capacity of two million passengers will be increased as part of plans to create a major transport hub for the northeast of Thailand.

The work is expected to commence in the 2018 financial year.