From Sunday, all international tourists flying to the South-East Asian country need to show proof of vaccination against Covid-19, or documentation of recovery from the virus.
Travellers will be asked to provide this proof before boarding flights with the airlines, which are responsible for ensuring they have the right documentation for travel.
Airline passengers who cannot provide proof of vaccination before flying will be subject to testing at their port of arrival.
The Civil Aviation Authority of Thailand confirmed the rule change on Sunday.
It comes as several countries around the world reimposed pandemic restrictions on travellers from China after it reopened its borders for the first time since the start of the global pandemic.
The US, India, Japan, Australia and France are among the nations that have set new rules requiring Chinese tourists to provide negative Covid-19 tests before admission.
Thailand is not asking visitors to show negative test results, or employing special restrictions on visitors from China. Instead, it is subjecting almost all international travellers to its new entry restrictions.
Visitors showing proof of recovery for entry must have had Covid-19 within 180 days and recovered no less than seven days before travel.
Authorities in Thailand recognise 16 vaccines, including AstraZeneca, Pfizer and Sinopharm. Travellers must have received a complete dose of the vaccine no less than 14 days before travel. A list of the approved vaccinations and the number of doses required are available on The Civil Aviation Authority of Thailand's website.
The amended rules do not apply to travellers under 18, Thai nationals or those transiting in Thailand.
Holidaymakers visiting Thailand from China or other destinations whose requirements might prevent their re-entry if they test positive while on holiday will also need to produce proof of a travel health insurance policy. Coverage must include a minimum of $10,000 for Covid-19 treatment during their planned stay, plus an additional seven days.
Thailand is preparing for an expected wave of tourists from China, with Thai tourism officials projecting about five million Chinese nationals will visit this year, according to Reuters.
China’s near total reversal of border controls that stemmed the spread of Covid-19 came into effect on Sunday, ending almost three years of strict entry requirements.