The association, which represents businesses, shops and hotels, said a prolonged rally would damage the economy and hamper confidence in Thailand for foreign tourists, investors and businessmen.
Its members plan to meet with police and other agencies if the protest in the area drags on, the RSTA said in a statement released on Monday.
The RSTA has deployed almost 2,000 security guards in the area from Chaloem Phao intersection to Central Chit Lom department store, Four Seasons Hotel and Novotel Bangkok Platinum Hotel, which is also covered by 1,500 security cameras.
The Ratchaprasong district attracts 250,000 tourists a day. It was severely damaged by red-shirt protesters in 2010.