Borrowing in the domestic market will be a major source of funding for the 2.4-trillion-baht infrastructure projects due to low interest rates, a source at the Public Debt Management Office says.
How much money will be secured from overseas markets depends on whether the Thai government receives special rates, the source said.
The government is negotiating with the Japan International Cooperation Agency, which provides cheap loans to fund infrastructure investment.
If foreign loans are cheaper than domestic sources after taking into account the costs of hedging against foreign currency risks, borrowing money abroad will be another source.
The government is set to borrow 100 billion baht in fiscal 2015, starting this month, to finance infrastructure projects until 2022.
They include dual-track railways, electric trains, water and air transport and four-lane roads aimed at upgrading Thailand as a logistics centre for Southeast Asia, lower transport costs and address traffic congestion in Bangkok.
Of the total funding, 44 billion baht will finance new projects and the rest will be used for ongoing projects.
The 44 billion baht will go to two lines of electric trains — the Green Line (Mor Chit-Saphan Mai-Khu Khot) with a length of 18.4 kilometres and the Red Line (Taling Chan-Min Buri) covering 39.6 km — and a dual-track rail route from Nakhon Ratchasima to Khon Kaen.
The 56 billion baht will be spent on ongoing electric train projects including the Purple Line (Bang Yai-Bang Sue), Blue Line (Hua Lamphong-Bang Khae) and Green Line (Soi Bearing-Samut Prakan).
Construction of the Pink Line and Yellow Line electric train routes will follow but await expropriation and environmental impact assessments, the source said.