Thai Prime Minister Prayut Chan-o-cha has offered consolation to the grieving families at the scene of Thursday's deadly gun and knife attack that has left the nation in shock.

Prayut laid flowers at a childcare center in the country's northeastern province of Nongbua Lamphu on Friday, where a former police officer went on a rampage the day before.

Local authorities say 36 people were killed and about 10 others were injured. The dead include 24 children aged between 2 and 5, who were taking a nap at the time of the attack.

The 34-year-old former police officer reportedly went home after the attack, and killed his wife and child before committing suicide.

Police say the man was dismissed from the police force earlier this year for drug possession and was facing trial. They say he was in court just before the attack, and a ruling was expected on Friday.

Investigators are trying to determine whether the trial was a factor behind the mass murder.

Buddhist monks and experts dispatched by the government are offering mental support to the bereaved families.

A man who lost his 4-year-old son said he wants to meet his boy again. He said he wishes the child will be reborn as his son again. He also said he lived away from his family due to work, but made video calls to them almost every day. He said he misses his son very much.

Flags are flying at half-staff at public facilities and schools across Thailand.

The country's King Maha Vajiralongkorn and Queen Suthida are due to visit the scene later on Friday.