Prime Minister Prayut Chan-o-cha is facing fresh protests from hundreds of kamnan and village heads across the country about a proposal which they say would abolish local administration.
The plan might affect the government's attempt to promote national unity, they say.
Protests have been reported in Phuket, Kanchanaburi and Ubon Ratchathani and come as the association of kamnan and village heads of Thailand sent a petition to Gen Prayut condemning the idea of elected local officials.
The association's move follows a Nov 25 proposal from the People's Democratic Reform Committee (PDRC) to the Constitution Drafting Committee (CDC) arguing that provincial governors and other local leaders, including kamnan and village heads, should be elected.
The PDRC also proposed that kamnan and village heads, who currently get to keep their positions for life, serve a maximum of two terms.
Under the local administration system, the government appoints officials, including provincial governors, to serve as its representatives to carry out state policies and oversee people's welfare. The plan would represent a huge shakeup of the sector.
The headmen expressed fears the PDRC's proposal may partly lead to the revocation of local administration, affecting provincial and district officials.
District chiefs could become a thing of the past, with kamnan and village heads next in line to receive the impact, said Suphot Bunhan, chairman of the association of kamnan and village heads in Ubon Ratchathani, who led 200 kamnan and village heads to rally in front of the provincial hall.
He said Thailand is not ready for elections at all levels because influential people could use their money to buy votes.
Under the current system, the government supervises provincial authorities. But some fear that if local officials have more freedom, they will skirt natural resource management and security policies.
Yongyot Kaeokhiao, chairman of the association of kamnan and village heads of Thailand, said the plan could lead to "disunity among people in society".
Rewat Khrueabutdimahachok, chairman of the federation of assistant district chiefs of Thailand, said that instead of uprooting local administration, the government should abolish the provincial administration organisations, which are not under the local administration system.
He accused them of poor performance and corruption.