The U-Tapao Rayong-Pattaya International Airport plans to begin construction of its second runway this year.
Chula Sukmanop, secretary-general of the Eastern Economic Corridor (EEC), said the project is now applying for a loan from the Asian Infrastructure Investment Bank (AIIB).
Mr Chula said Italian-Thai Development (ITD) has been selected as the project contractor.
Tharit Issarayangyun, EEC deputy secretary-general, said the project is being planned in collaboration with the Royal Thai Navy (RTN).
Mr Tharit added that the second runway will be 3,505 metres long and located 1,140 metres from the current runway.
The second runway is expected to service at least 70 flights an hour and accommodate large aircraft.
The project investment is around 15.2 billion baht in total, said Mr Tharit.
However, the EEC has raised concerns about the delayed construction of the high-speed railway connecting three airports -- Don Mueang, Suvarnabhumi, and U-Tapao.
The high-speed rail system, an EEC flagship project, has a contract signed with the State Railway of Thailand (SRT) and Asia Era One, a Charoen Pokphand (CP) Group subsidiary. The project is now being negotiated and expected to wrap up this month.
According to Mr Chula, the design and construction plan for the high-speed rail tunnel will have to pass under the second runway. The tunnel's design has already been completed.
Construction of the runway is expected to take 36 months. The contract stipulates that the high-speed rail tunnel must be completed within 18 months from the start of the runway contract between the RTN and ITD.
Mr Tharit said the EEC and the RTN have discussed if the high-speed train tunnel under the runway cannot be completed by early 2025, the EEC will have a proposal to cut the work from the joint venture contract with Asia Era One and have the SRT carry out the construction of the railway tunnel instead.
He said this was to avoid affecting the construction of the airport runway.
"The SRT and Asia Era One have been informed about this issue. Everyone knows what the solution is," Mr Tharit said.
"The length of the high-speed rail tunnel segment that passes beneath the runway and into the passenger terminal is roughly three to four kilometres. The estimated cost of building it is 10 billion baht."
Meanwhile, Weerawat Phantawangkul, CEO of U-Tapao International Aviation, said the airport development plan is expected to begin next year, with construction lasting at least five years.
He said three building projects are planned for a 6,500-rai area, and at least 100 billion baht should be invested in the first phase of the renovations.
