Thailand is observing state-level mourning on Friday in memory of the 38 people killed, mostly children, at a day-care by a former policeman.
Prime Minister Prayut Chan-o-cha directed that all national flags be flown at half-mast for the day in order to express condolences to the victims' families.
Pol Corporal Panya Kamlarb, a 34-year-old former cop, carried out a gun and knife attack on a day-care center, killing 38 people, including 22 children.
After the attack, he killed his wife and their child before committing suicide.
The deadly incident happened on Thursday around 12:50 p.m. (0550GMT) in the upper northeastern province of Nong Bua Lam Phu at the day-care home housed in the office of the Uthai Sawan Tambon Administration in Naklang district.
Twelve more people were injured and are being treated.
The attacker was a former policeman with a history of drug abuse, Thai police said.
During a late-Thursday night visit to the Udon Thani provincial hospital to see injured 3-year-old Krisakorn Riangcharoen, Thai Privy Council President General Surayud Chulanont said the country’s king will take all injured victims under his sponsorship until they all recover.
The massacre triggered an outpouring of global solidarity and condolences.
UN Secretary-General Antonio Guterres expressed deep sadness over the "heinous shooting."
“Learning centers should be spaces where children feel safe, never targeted,” he tweeted.
Thai King Maha Vajiralongkorn and Prime Minister Prayut are expected to pay a visit to the families of the victims in Nong Bua Lam Phu province.
In addition, the government has decided to provide financial assistance to each victim's family.
“No dry eye in the hall where families of victims murdered in the childcare centre in Nong Bua Lamphu province Thailand are gathered,” journalist May Wong tweeted from the massacre site, where families of the slain have gathered in front of the day-care center.
“It’s a very difficult scene to witness,” she added.
The gunman was "apparently under the influence of drugs," Pol Maj Gen Paisal Luesomboon told Thai public broadcaster PBS News on Thursday.
He was discharged from services last year on the basis of drug abuse, he added.
Kamlarb was armed with a shotgun, a pistol, and a knife.
The mass shooting has also triggered a debate about the possession of handguns in Thailand, a member of the Association of Southeast Asian Nations (ASEAN).
Data by Small Arms Survey shows the Buddhist-majority kingdom has the highest number of guns in possession of private individuals, with 10,342,000 guns recorded in 2017, among the 10-member ASEAN bloc.