The Energy Ministry says liquefied natural gas (LNG) imports will double to 40 million tonnes a year by 2036 from the current forecast if the country fails to diversify its power mix and relies too much on gas.
According to the country's 2015 power development plan, Thailand is scheduled to import 20 million tonnes of LNG in 2036, up from an estimated 3 million tonnes this year.
But LNG imports are set to spiral in the absence of a broader power mix.
In response, Thailand will diversify by trimming the share of gas in power generation from 70% to 30% by 2036, said Sarawut Kaewtathip, director-general of the ministry's Policy and Strategy Coordination Office.
Thailand will also try to raise the proportion of coal to 25% from the current 20% and increase the contribution of renewable energy to 20% from 8%.
The proportion of power bought from neighbouring countries would rise to 20% from the current 10% as a way to cut reliance on gas.
The first lot of imported coal is tipped for coal-fired power plants in Krabi and Songkhla provinces with a combined capacity of 3,000 megawatts.
These projects are undergoing assessment for their environmental and health impacts.
A heavy dependence on gas for power generation is expected to deplete domestic gas resources by 11% each year.
New petroleum exploration in Thailand has been delayed since 2008 by protests from non-governmental organisations that want a change in the licence-granting system from the existing concession scheme to a production sharing arrangement.
In comparison with Thailand, Malaysia uses gas for 8% of its power needs and coal for 42%, Mr Sarawut said.
For Indonesia, the mix is 18% from gas and 59% from coal, while the Philippines gets 25% from gas and 47% from coal.
Another reason for Thailand to cut its reliance on gas is the frequency of supply disruptions over the past few years, Mr Sarawut said.
Disruptions have occurred more often in recent years as a result of maintenance shutdowns, especially by neighbouring Myanmar, whose demand for gas to serve its own growing economy is about to rise as well.
"We expect to suffer more frequent gas disruptions due to ageing petroleum rigs that need more frequent maintenance," Mr Sarawut said.
He noted Thailand's strong potential for development of renewable energy from agricultural waste through biomass, biogas and waste-to-energy projects.
Biomass and solar power are main components of the country's plan to increase the proportion of renewable energy to 20% by 2036.