The clashes took place as demonstrators attempted to obstruct the registration of party-list candidates in the February 2 general election this morning at Thai-Japanese sports stadium.
The slain policeman was identified as Pol Sen Sgt Maj Narong Pitisit, 45, from Taladplu Police Station. He was shot in the chest while on duty at Gate 3 of the stadium in Din Daeng.
Seriously wounded, he was pronounced dead at hospital.
The number of injured police officers has risen to 25.
Erawan Emergency Centre director Dr Petchpong Kamjornkitjakan reported that 97 persons were wounded in clashes between police and anti-government protesters.
Those injured were sent to several hospitals. A guard of the Network of Students and People for Reform of Thailand (NSPRT) who was shot in his head is now hospitalised in the Intensive Care Unit after the operation.
A Japanese reporter was also hurt in the head and is now in Rajvithi Hospital, while a reporter from Thai Rath newspaper was under medical care at the Veterans General Hospital.
The Centre for the Administration of Peace and Order (CAPO) announced that 14 suspects have been detained for investigation for allegedly inciting unrest, intruding the state office and obstructing the election process.