An announcement in the Royal Gazette on Sunday said people living in Chonburi, Ayutthaya and Chachoengsao provinces will not be allowed to go outside unless necessary from Tuesday onwards.
It added that a curfew will be imposed from 9pm to 4am, while checkpoints will be set up to prevent people from travelling outside their provinces.
Bangkok and nine other provinces have already been under these restrictions, the toughest in more than a year, since last Monday.
Thailand is currently battling its longest-running and most severe outbreak so far. The country reported 11,397 infections and 101 deaths on Sunday, bringing the cumulative total to 403,386 cases and 3,341 fatalities.
Most of Thailand’s deaths and infections have been recorded since April, due to an outbreak fuelled by the highly transmissible Alpha and Delta variants.
The surge has overwhelmed hospitals, strained the economy and thrown tourism recovery plans in doubt.
In a bid to contain the outbreak, Thailand on Friday imposed a nationwide ban on public gatherings, with a maximum penalty of a two-year jail term or a fine of up to 40,000 Thai baht ($1,220) or both.
The country’s vaccine rollout meanwhile remains sluggish due to supply problems.
Just 5 percent of Thailand’s population has been fully vaccinated and health authorities said last week that they will seek to impose limits on exports of the locally produced AstraZeneca vaccine because the country does not have enough for its own needs. (Al Jazeera)