The Public Health Ministry on Thursday reported 60 new cases of novel coronavirus disease (Covid-19), raising the total to 272, and said the infections were transmitted at entertainment venues, including boxing stadiums.
It was the largest increase to date.
In the ministry's daily Covid-19 update, Dr Suwannachai Watanayingcharoenchai, director-general of the Disease Control Department, said the new cases were in two groups.
The first group of 43 people were either in close contact with previous patients or visited the places where patients had been. They consisted of 12 visitors to boxing arenas, 14 to other entertainment venues, 12 people in previous close contact with Covid-19 patients, and five attendees at religious ceremonies in Malaysia.
The second group comprised 17 people - nine returnees from other countries, three people working closely with foreigners, one person who had been in crowded areas, and four whose cases were under investigation.
Dr Suwannachai asked people going to boxing stadiums and entertainment places to show respect for society by practising self discipline, to help contain the disease.
"The new patients are workers at entertainment places, visitors to those places and their family members.
"They have been detected since March 12, and there are 57 of them.
As for the people visiting boxing stadiums, infections include promoters, boxing camp owners, trainers, commentators and spectators, members of their families and people close to them.
"Since the first report for this group on March 14, there have been 52 of them," Dr Suwannachai said.
"Spectators came from other provinces. After being infected, they returned home and transmitted the disease to people close to them and their families. Importantly, those who are not ill are not quarantining themselves as the Public Health Ministry has advised. They continue their activities, and this is very dangerous to other people.
"This is mainly why the Public Health Ministry advises people to avoid crowded places, which are high-risk areas."
Dr Suwannachai said people should not go out unless it was necessary.
Of the 272 local Covid-19 cases so far, 42 had recovered and were discharged, 229 remained at hospitals, including three critically ill patients, and one had died.
Patients under investigation totalled 8,157, 63% of whom recovered and had suffered mostly from seasonal flu.
The Public Health Ministry also reported that global Covid-19 cases numbered 212,799 with 8,787 deaths in 168 countries, including 80,894 cases and 3,237 deaths in China.