Leaders of the People's Alliance for Democracy (PAD) said they had begun clearing stages from the secondary site near the United Nations headquarters, to let royal motorcades through.
But protesters were continuing their long-running occupation of Government House, ignoring requests to leave ahead of two royal functions and the ASEAN regional summit next month.
'We unanimously agreed to permanently withdraw from Makawan Bridge, but will continue to rally inside the Government House,' said Chamlong Srimuang, one of the senior PAD leaders.
The PAD launched its campaign to bring down the democratically elected government in May, claiming it was running the country on behalf of ousted prime minister Thaksin Shinawatra, whom they accuse of corruption and nepotism.
Thousands of PAD supporters stormed the prime minister's offices - known as Government House - in late August, and have stayed there ever since, setting up tents, food stalls and stages.
Prime Minister Somchai Wongsawat has urged them to leave ahead of the funeral for the king's sister, Princess Galyani, in November, and the king's birthday and a key regional summit in December.
Preparations and rehearsals have already begun for the grand cremation ceremony for Princess Galyani, who died in January this year. The official six-day funeral will begin on November 14.
Mr Chamlong said the PAD would continue its occupation of Government House until its demands are met.
'Our goal is still unchanged - we oppose any change to the constitution and the government must step down to pave the way for new politics,' he said.
The PAD's so-called 'new politics' have been loosely defined by their leaders as a system of government with fewer elected lawmakers in parliament.
The campaign erupted into violence earlier this month when police fired tear gas at thousands of protesters trying to block parliament. Two people were killed and nearly 500 injured in the clashes. -- AFP