The letters and the four red post boxes from the protest in Bangkok yesterday are in police possession, at the Chanasongkram police station.
Deputy Metropolitan Police Bureau commissioner, Police Major General Piya Tawichai, said whether anyone will be charged for writing those letters depends on whether the content violates any law.
Piya also said, regarding what seems to have been a smoke bomb thrown at the protest site yesterday, that the matter is still under investigation.
Regarding the use of water cannons against the protesters yesterday, Piya said everything was done according to the rule of law. The water cannons were used after a warning was issued not to approach the police front line. The water was shot in a spray, not directly at the protesters, and it did not contain any chemicals, he said.
Piya said the protest yesterday was in violation of the Public Gathering Act. The protesters did not submit a request seeking permission to hold the demonstration. The police are investigating and gathering evidence and witnesses before making a decision whether to charge anyone with an offence. He added that the protest yesterday covered the jurisdiction of four different police stations; Nang Loeng, Chanasongkhram, Samranrat, and Phra Ratchawang.
Source: Thai Public Broadcasting Service (Thai PBS)