The Constitutional Court has accepted for consideration a petition seeking its ruling on whether the Power Development Plan (PDP) for 2018-2037 is constitutional.
The move has sparked concern over potential damage to investment plans in the electricity industry if the court rules against the plan.
The petition was lodged by Sudhiporn Patumtaewapibal, the former rector of Assumption University. He asked the court to rule if the plan violated Section 56 of the 2017 charter.
This stipulates that the government's infrastructure and utility businesses are necessary for the country's security and the government cannot allow the state sector's ownership of such businesses to fall below 51%.
In the petition, the complainant argues the PDP for 2018-2037 would reduce the state's power generation capacity to below 51% of total national power generation.
The court said it accepted the petition because it met the filing criteria. It has ordered the Energy Ministry to submit clarification within 15 days of receiving a copy of the petition.
Earlier, Mr Sudhiporn asked the court to rule on the constitutionality of the plan via the Office of the Ombudsman, which reviewed his petition and agreed that state power generation fell below the 51% threshold.
The office said it believes 51% ownership means the state must have this in each of three categories: power generation, power transmission and power distribution.
Even though the state purchased electricity from other private power generators, and transmitted and distributed this to the public, the 51% rule as required by the constitution was not met, it said.
The Energy Ministry has defended the PDP, saying firms were allowed to enter the power generation sector to increase efficiency and competition, but were not allowed to own power infrastructure and had to sell the output to the state.
It said the state-run Electricity Generating Authority of Thailand (Egat) was responsible for 30% of the country's power generation as of November 2019, whereas private power producers in which Egat was the major shareholder accounted for 14%.
The 45% of power generated by private firms breaks down as 17% by independent power producers (IPP), 20% by small power producers (SPP) and 8% by very small power producers (VSPP). The other 11% was imported.
