The number of Covid-19 inpatients rose to 1,811 last week (from April 23 to 29), up from 1,088 in the previous week, and related deaths doubled from five to 10 over the same period, according to the Department of Disease Control (DDC).
These figures increased two weeks after the Songkran festival in mid-April and are expected to go up further when the new school term and the rainy season start this month.
On April 29, 157 Covid-19 patients suffered from lung inflammation, up from 73 on April 22. Of the new patients, 79 of them were dependent on ventilators, up from 35.
From Jan 1 to April 29, Thailand registered 8,383 Covid-19 inpatients and 288 related fatalities.
Government spokesman Anucha Burapachaisri said on Tuesday that the DDC expected the number of Covid-19 inpatients to soar during the upcoming rainy season, along with influenza outbreaks.
Prof Dr Yong Poovorawan, chief of the Center of Excellence in Clinical Virology at Chulalongkorn University, wrote on Facebook that the coronavirus has become a seasonal disease and will start to spread at the beginning of the rainy season when school resumes.
According to the Meteorological Department's forecast, the country will fully enter the rainy season from the middle of this month.
Election campaigns, which may draw large crowds, would be another factor in the spread of the disease, Prof Dr Yong wrote.
Dominant variants continue to be linked with Omicron, a variant with less severity, he wrote.
The elderly, pregnant women and those with underlying illnesses are more vulnerable to becoming seriously ill and/or dying from Covid, warned the virologist.
Prof Dr Yong advised those who are vulnerable to receive Covid-19 vaccination before the rainy season starts.