The decision could lead to the resumption of some measures activated by health authorities when the country was facing its worst moment due to the pandemic.
The shift from level 3 to 4 (of five levels) could imply the closure of places with high risks of contagions and the resumption of other regulations, Permanent Secretary at the Ministry of Health Kiattiphum Wongrajit said.
Thailand has reported nearly 5,500 Covid-19 cases in the past few days, almost 50 percent more than two weeks ago.
Besides China, it was the first country where the disease was detected (in early 2020) and the first nation in Southeast Asia hit by the Omicron variant (December 6).
According to its latest report, there were 5,775 cases and 11 deaths, so the total number of cases rose to 2,245,250 and the death toll soared to 21,780.