The Civil Aviation Authority of Thailand (CAAT) on Saturday (May 16) extended the ban on international flights from 12.01am of June 1 to 11.59pm on June 30.
The announcement cited the need to continue measures for preventing the spread of Covid-19.
Its previous diktat on April 27 had banned international flights from May 1 to 31.
However, state or military aircraft, emergency landings, technical landings, humanitarian and relief flights, as well as cargo aircraft, will be exempted.
The CAAT on Friday (May 15) decided against reopening Phuket International Airport from 12.01am on May 16 given the lingering risk of a Covid-19 outbreak. The airport will remain closed until further notice, the CAAT said.