BANGKOK - Thai police braced for a fresh round of anti-government protest in Bangkok on Sunday amid security concerns in a city where multiple rallies over recent years have led to unrest.
Stages were erected and some early demonstrators milled near the planned rally site, a park in the centre of the capital.
"The situation is normal. Police will take care of security during the protest," said deputy metropolitan police chief Parinya Chansuriya, adding that there was as yet no official estimate for the numbers expected.
The protests are being held by the self-styled "People's Army" - a coalition of ultra-royalist groups who loathe the Puea Thai ruling party and its self-exiled figurehead Thaksin Shinawatra.
Prime Minister Yingluck Shinawatra, Thaksin's sister, on Saturday expressed "worry that the rally could lead to violence".
The Thai government has already invoked a special security law to control the protests, which could go on for several days. More than 1,600 police were deployed Saturday to protect key government buildings, while thousands more were put on standby.
Police have said the special security law does not extend to the park area, but that they are authorised to use water cannon, tear gas and rubber bullets if violence erupts.
Mass demonstrations, often involving bloodshed, have become a recurrent feature of Thailand's turbulent politics in recent years, with ultra-royalist nationalist "Yellow Shirts" and their pro-Thaksin "Red Shirt" foes both taking to the streets.
In 2010 two months of Red Shirt protest against a previous government brought much of Bangkok to a standstill and culminated in a bloody military crackdown.
Some 90 people were killed in the unrest, with around 1,900 injured.
Sunday's protesters are targeting a government-backed bill, due to enter parliament on August 7, which proposes an amnesty for those involved in political violence since a 2006 coup that toppled Thaksin.
The country has been riven by political tensions since the overthrow of Thaksin, a deeply divisive figure who lives abroad but still draws loyalty among the kingdom's poor, rural working class.
The contentious amnesty bill would scrap charges against protesters involved in incidents from the September 2006 coup until May 2012 - barring the leaders.
An attempt to introduce an amnesty bill last year was aborted after Yellow Shirts - who support the opposition Democrat Party - rallied outside the legislature.
The Yellows, who boast support from Bangkok elites and elements in the military, helped unseat Thaksin and claimed the scalps of two allied governments in under five years.
Their 2008 rallies paralysed Bangkok's main airports stranding thousands of tourists.