Workers began constructing the pyres, which are 2.3 metres long, 80 centimetres wide and 80cm high, at Wat Rat Samakkhi in Tambon Uthai Sawan, Na Klang district in the northeastern province.
The royally sponsored cremations will be held on Tuesday.
The construction work, a joint operation by the temple and local agencies, used 20,000 bricks, 2 tonnes of cement and five truckloads of sand.
Phrakhru Adisai Kijjanuwat, abbot of Wat Rat Samakkhi, said the funeral rites will begin at 9am on Tuesday and culminate with the cremations at 8pm.
The abbot said each pyre will be covered to avoid further traumatising parents and relatives of the victims.
After the cremations, the pyres would be dismantled and the area returned to normal use by the community and temple, he added.
The abbot said this would be the first mass cremation at the temple and hopefully the last.
Sacked police officer Panya Khamrab killed 36 people in a deadly rampage that began in the nursery as the toddlers were taking a midday nap on Thursday. He then murdered several more victims on his way back home, including his wife and son, before turning the gun on himself.
On Monday, workers at Wat Sri Uthai were connecting an electric furnace borrowed from Samut Sakhon for the mass cremation.
Chanpen Dejpok, head of Moo 1 village, confirmed the temple is conducting prayers for the 11 victims, but relatives of Panya’s wife and three-year-old son would move the bodies for cremation back home.
The United Nations child agency, Unicef, has issued a statement expressing its sorrow and shock at the mass killing of young children.
“Unicef condemns all forms of violence against children. No child should be a target or witness of violence anywhere, anytime,” the statement said.
“Early childhood development centres, schools and all learning spaces must be safe havens for young children to learn, play and grow during their most critical years.
“UNICEF sends its heartfelt condolences and deepest sympathies to the families who lost loved ones and the injured. We join all people in Thailand in mourning and hope that those affected receive appropriate and timely support.”
On Sunday, Pope Francis prayed for the grieving families of victims of the massacre, the Catholic Social Community of Thailand (CSCT) said.
"We pray for the dead in Thailand's tragedy, especially innocent children, and [may they be sent] to His arms," Pope Francis prayed, as quoted by the CSCT. "We also pray that God may grant unity to the grieving families and the injured.”