Thailand has the highest risk among Asean countries for skyrocketing energy import bills unless concrete measures can be taken to address rising local consumption and depleting reserves, according to the International Energy Agency (IEA).
Its Southeast Asia Energy Outlook report released Wednesday predicts Thailand's net oil and gas import bills will hit US$100 billion in 2035, more than triple the $30 billion in 2011.
The region's energy demand will rise by 80% between now and 2035 to support a near tripling of the regional economy and population growth of 25%.
Meanwhile, a decline in mature fields and limited large new prospects will lead oil production across the region to fall by almost one-third.
Consequently, the region will become the world's fourth-largest oil importer, after China, India and the EU.
The region's spending on net oil imports will triple to $240 billion in 2035 or 4% of gross domestic product (GDP).
Indonesia, which looks on track to spend the same amount for oil imports as Thailand in 2035 at $70 billion, will receive a partial offset of $30 billion from gas exports.
"Thailand and the Philippines have very limited indigenous oil and gas resources and are seeing their net import dependencies rise to extremely high levels," said the IEA report.
Energy permanent secretary Suthep Liumsirijarern said even though the Philippines, with a population of 98 million, has more people than Thailand, oil consumption in the countries is similar.
But Thailand consumes more gas, mainly for power generation, he said.
"The outlook going towards 2035 is that Thailand will be the most at risk in terms of energy security unless no concrete action is taken. The Philippines is at the highest risk," said Mr Suthep.
IEA executive director Maria van der Hoeven said Thailand is the leader in Asean in terms of actually having an energy efficiency action plan.
But implementation is the key, or else the plan is nothing more than a piece of paper, she said.
Interconnection with neighbouring countries would enhance energy security.
The IEA estimates $1.7 trillion worth of cumulative investment in the energy supply infrastructure is required in Southeast Asia between now and 2035, 60% of it in the power sector.
An additional $330 billion is needed to improve end-use efficiency.
In return, a savings of nearly $500 billion will be realised and help to boost regional GDP by 2% in 2035. "Phasing out fossil-fuel subsidies remains unfinished business in Southeast Asia, with subsidies amounting to $51 billion in 2012. Despite recent reform efforts, notably in Indonesia, Malaysia and Thailand, subsidies remain a significant factor distorting the energy market," said the report.