Protesters began marching to the German embassy on Monday evening, to ask Berlin to look into the matter of His Majesty the King living in Germany.
The pro-democracy movement gathered at Samyan intersection about 5pm and started marching on Rama IV Road to the embassy on Sathorn Road.
They said earlier that they would petition the German government through the embassy to look into whether the King had violated German sovereignty by exercising his power on German soil.
The German embassy on Monday released a statement written on Sunday stressing the need for a peaceful gathering by the protesters and protection of its premises by the government under the Vienna Covention.
The embassy said it would be ready to receive the petition and convey it to Berlin on condition it was conveyed in a "peaceful manner".
"As in previous instances, the embassy is ready to receive messages addressed to the Federal Goverment, conveyed in a peaceful manner," the statement said.
The rally ended at around 9pm after a co-leader told protesters the ambassador said he would forward their letter to the German government.
A rally outside the embassy in support of the monarchy earlier on Monday ended after presenting a letter addressed to the ambassador.
