The Energy Ministry plans to hike prices for diesel and natural gas for vehicles (NGV) gradually next year in preparation for the Asean Economic Community (AEC).
Energy Minister Pongsak Raktapongpaisal said PTT Plc, the national oil and gas conglomerate, has been assigned to study energy price structures next year ahead of establishment of the AEC in late 2015.
The study is expected to be complete by mid-December.
Diesel prices have been kept at no more than 30 baht a litre, while NGV is traded at 10.50 baht a kilogramme.
Critics say price fixing will encourage more fuel smuggling to neighbouring countries where prices are higher when the AEC allows freer flows of goods in Asean.
"We need to increase the prices of diesel and NGV, but measures will be introduced to minimise the impact on consumers' cost of living including taxi fares and other transport costs," said Mr Pongsak.
The ministry has discussed the planned price hike with transport associations.
Price discounts will be offered to taxis, while PTT will provide support for trucks to switch to liquefied natural gas from diesel.
In other news, Mr Pongsak said the supply disruption of natural gas from Myanmar's Yetagun gas field from Dec 25-Jan 8 will cause six power plants in Thailand to suspend operations during the period, affecting a combined generating capacity of 6,400 megawatts.
But he said no significant impact is expected, as power consumption is normally low during this period and the scheduled maintenance of natural gas platforms in the Gulf of Thailand has been postponed to manage the supply shortfalls.
However, the 28-day shutdown of the Thai-Malaysia Joint Development Area (JDA) next June and July is a concern, as electricity demand in southern Thailand is quite high at 2,500 MW.
Without the supply from the JDA, the 700-MW Chana power plant in Songkhla province will need to be shut down and a backup plan will be outlined, he added.