Over 30 activists have gone on a hunger strike to press the government into cancelling plans to build two coal-fired power plants in Krabi and Songkhla.
The activists have vowed to maintain their strike outside the United Nations headquarters on Ratchadamnoen Avenue until both projects are scrapped.
They are members of the Network of People from Songkhla-Pattani against the Coal Power Plant, and the Save Andaman From Coal groups.
Last week, local people opposing the plant in Songkhla's Thepha district called on the Energy Ministry to withdraw its Environment and Health Impact Assessment (EHIA) study.
The call followed the ministry's announcement that it had decided to postpone the start date for construction of the plants by another three years so more studies could be carried out.
The Krabi plant finished its EHIA report in early 2016 and was awaiting word from the government on a start date for construction.
However, the Electricity Generating Authority of Thailand (Egat) was ordered to revise the EHIA in April of that year. The plant will have a capacity of 800 megawatts. Operations are due to begin in 2025.
The other site is the 2,000MW Thepha plant, which is near to wrapping up EHIA approval. While a start date for construction remains elusive, the plant is scheduled to open in 2024.
Amid lingering concerns about pollution and other unwelcome byproducts of the plants, Egat was authorised to survey both sites to determine if they were warranted.
Some 33 activists began their fast at 11.30am Monday, describing it as an act of civil disobedience and vowing to only drink water until their demands were met. More people are expected to join the campaign, the groups said.
On Jan 29, the groups rallied outside Government House.
At the same time, local residents in Songkhla presented a petition to Prime Minister Prayut Chan-o-cha during his mobile cabinet meeting to the southern province recently. It called on the government to axe the project.
The protesters in Bangkok were warned to cease such activities as they were in breach of a ban on staging protests within 50 metres of Government House.
The protest has continued despite the warning. Some activists split up and converged in front of the UN office ahead of the hunger strike.