Thousands of Red Shirt protesters have blocked a major intersection in Bangkok to mark six months since Thai security forces crushed a protest in the same area resulting in 91 deaths.
Although the protest in the heart of the city is illegal under the state of emergency still in force, police have allowed it to proceed, the ABC reports.
Army chief General Prayut Chan-O-Cha warned anyone inciting social rift with inappropriate T-shirts or placards would face two years in jail.
There have been rousing speeches about the lack of democracy and demands to release 19 protest leaders still in jail charged with terrorism.
The protest leaders say they are not attempting a new sit-in and all the demonstrators will leave peacefully after the speeches.