Despite the warning to protesters, the junta offered a reprieve to the country's vital tourism industry. It lifted the military's curfew at three popular beach resorts – Phuket, Koh Samui and Pattaya – to ease the impact of the May 22 coup on tourists.
A midnight-to-4 a.m. curfew remained in effect for the rest of the country, including Bangkok, where the raised arm salute was unveiled over the weekend as an unofficial symbol of opposition to the coup.
"At this point we are monitoring the movement," Col. Weerachon Sukhondhapatipak, a spokesman for the junta, told The Associated Press. "If it is an obvious form of resistance, then we have to control it so it doesn't cause any disorder in the country."
Since staging its bloodless coup, the military has prohibited political gatherings of more than five people and tried to enforce a ban on criticism of the coup by closing politically affiliated television stations and blocking hundreds of websites.
On Sunday, authorities deployed nearly 6,000 soldiers and police in Bangkok to prevent planned protests against the coup. Amid the heavy security, creative forms of protest emerged. Some people wore masks as they walked through a central shopping district. Others joined small flash mobs, or stood alone, and flashed three fingers in the air.
Asked what the symbol meant, protesters have given varying explanations. Some say it stands for the French Revolution's trinity of values: liberty, equality, fraternity. Others say it means freedom, election and democracy. A photo montage circulating online paired a picture from the science fiction blockbuster The Hunger Games with a graphic of three fingers labeled, 1. No Coup, 2. Liberty, 3. Democracy.
In the movie series and the book trilogy it is based on, the salute is a symbol of rebellion against totalitarian rule and stands for: Thank you, Admiration and Goodbye to someone you love.
"We know it comes from the movie, and let's say it represents resistance against the authorities," Weerachon said, noting that if Thai authorities encounter the salute they will first ask protesters to stop.
"If a single individual raises three fingers in the air, we are not going to arrest him or her," he said. "But if it is a political gathering of five people or more, then we will have to take some action."
"If it persists, then we will have to make an arrest," he said.
Thailand has been calm since the army overthrew the nation's elected government on May 22, saying it had to restore order after seven months of demonstrations that had triggered sporadic violence and left the country's political rivals in a stalemate.