Police today asked Ratchaburi Court for a warrant to arrest a suspect in the shooting.
Pol Lt Gen Thana Chuwong, the Provincial Police Region 7 commissioner, identified the suspect as Wanchart Niamraksa, a member of the Ratchaburi provincial administration organisation.
Pol Lt Gen Thana said Mr Wanchart would be charged with murder, attempted murder, having firearms and ammunition in possession without permission and carrying them in public without proper reason.
The shooting was believed to have been motivated by local politics and personal conflict, he said.
The attack occurred about 7pm at Wat Tha Kham in Moo 7 village of tambon Sam Ruan. The mourners were seated in an open prayer hall.
Five people were hit by bullets.
Police called to the scene found the hall a mess, with toppled chairs, abandoned possessions and blood splatters.
Those wounded were Yingpan Kanket, kamnan of tambon Don Sai, and four candidates in the March 28 election for the municipal council of tambon Don Sai - Varaporn Niamraksa, Nakhon Wanpen, Somthawil Srirat and Monthien Jaitham.
The wounded were admitted to Ratchaburi, Chet Samian, Bangkok-Ratchaburi and Mahachai hospitals.
Mrs Varaporn, who was running for mayor of the municipality, was later pronounced dead at the hospital.
Police said two spent .22 cartridges and one 11mm spent shell had been found at the scene.
Eyewitnesses said Mr Yingpan, as sub-district chief, had been asked to light joss sticks and candles before a Buddha image to mark the opening of the ceremony. As he did so, there was a barrage of gunfire. Amid the ensuing panic, people were heard yelling out for everyone to lie flat on the floor.
When the gunfire ended, five people people were found to have been hit.
Witnesses told police the shots were fired from behind the main Buddha image. The number of attackers was not known.