Thai villagers were arrested amid protests against government plans for an industrial estate in the south of the country.
Hundreds of locals from Songkhla province close to the border with Malaysia converged on the government house in Bangkok over a disowned memorandum of understanding between Chana villagers and a former minister to scrap the proposed Chana industrial complex.
Prime Minister Gen Prayut Chan-o-cha said the MOU was invalid and that agreements with any group would need the formal approval of the Cabinet.
Thirty-six protesters from the area who arrived in Bangkok on Monday were arrested by riot police on the same night.