Covid-19 infections in the capital are surging, with approximately 2,000 cases per day, says the Department of Disease Control (DDC).
Many of the infections are among adolescents and the working-age population, it said.
Dr Suthat Chottanapund, director of the department's Institute for Urban Disease Control and Prevention, said daily infections are increasing in all areas of the capital to 1,800-2,000 cases per day.
The main cause has been close contact with infected patients through group activities conducted in venues with poor airflow, such as pubs and bars which have obtained restaurant licences.
The DDC recorded 28,256 Covid-19 cases in the capital from Dec 12 to Feb 8, of which 31% were in the 20-29 age group. Some 21% were aged 30-39 and 15% were 40-49.
"We have found the main cause of infections remains unchanged, and we have seen more infections within families as the Omicron variant is easily spread," Dr Suthat said.
He said the number of daily deaths had dropped from five to 10 to just one or two cases a day.
Senior citizens, unvaccinated people and those living with chronic diseases still account for most deaths.
Department of Health chief Suwannachai Wattanayingcharoenchai warned people who frequent fresh markets to ensure they take precautions, as many clusters have been found there.
He said fresh markets should follow ministry guidelines in terms of preventive measures, especially social distancing, wearing masks and frequent hand washing.
The latter is still considered important as the virus can remain on banknotes, coins, products and plastic bags, he added.
There were 13,182 new Covid cases recorded nationwide on Wednesday, including 40 among prison inmates and 139 imported cases, with 24 fatalities, according to the Public Health Ministry.
The 139 imported cases included 51 from Russia, nine from Kazakhstan, eight each from Germany and France, and six each from Estonia and Ukraine.