Due to the widening price gap between local and foreign LPG, refineries have an incentive to export the gas. Now the department plans to levy export tariffs on exported gas in order to ensure no shortage in the Thai market.

"However, as the world LPG price is about US$460 (Bt16,198) per tonne while the local price is maintained at no more than US$315 per tonne, we are not sure that the tariff would be effective in discouraging exports," said director-general Metta Banterngsook.

The department will monitor how the tariff affects exports. If the volume drops, it means the measure is effective.

The Energy Ministry has made agreements with LPG traders whereby they should export the gas only when domestic supply is sufficient. The tariff collection is imposed as an additional measure to ensure sufficient supplies.

"The measure is necessary given that gas consumption among vehicles is rising and we're afraid that we might experience shortages," said Metta.

LPG consumption is on the rise due to there being more LPG gas stations than natural gas vehicle (NGV) stations. Once the number of NGV stations expands, more consumers should switch to natural gas, added Metta.