The government on Monday recorded 9,635 new Covid-19 cases -- by far Thailand's biggest one-day increase since the start of the pandemic -- along with 25 Covid-related deaths.
Of the new cases, 6,853 were found in prisons, according to the Centre for Covid-19 Situation Administration -- 71% of the daily increment.
The accumulated death toll in Thailand is now 614, with 111,082 coronavirus infections logged since early last year -- meaning the new cases announced on Monday amounted to an almost 10% increase in the historical caseload in a single 24-hour period.
Data from the Centre for Covid-19 Situation Administration (CCSA) showed that prisons in Chiang Mai and Bangkok held the most infected inmates.
Aside from the 6,853 new prisoners diagnosed with Covid-19, Bangkok led new transmissions with 1,843 cases, followed by Samut Prakan (155) and Pathum Thani (146).
CCSA spokesman Taweesilp Visanuyothin said the biggest concern was a continued surge in Bangkok with 28 clusters in 19 districts.
They were Din Daeng, Wattana, Klong Toey, Lak Si, Lat Phrao, Ratchathewi, Phra Nakhon, Promprap Sattruphai, Suan Luang, Pathumwan, Sathon, Samphanthawong, Chatuchak, Bang Rak, Prawet, Wang Thonglang, Ramkhamhaeng, Bangkok Noi and Huai Kwang.
Attempts to contain the virus in Bangkok were still focused on a residential camp for construction workers in Lak Si, he said.
The campsite — comprising 19 makeshift living quarters, each with two floors — was set up for labourers working for a project of Italian Thai Development Plc at nearby Chulabhorn Hospital.
The area was sealed off, with nobody allowed to enter or exit for 14 days starting on Sunday, he said. Authorities were tracking labourers hired by 11 subcontractors working on the project for fear they could spread the virus to other areas, the spokesman said.
The 25 additional deaths logged on Monday comprised 18 in Bangkok and one each from Suphan Buri, Sukhothai, Samut Sakhon, Samut Prakan, Nonthaburi, Nakhon Sawan and Chai Nat.
The government also recorded nine imported cases: four from Malaysia, two from Cambodia and one each from Pakistan, Ireland and Israel.