BANGKOK (BLOOMBERG) - Thailand's aviation regulator said airlines should ask passengers coming from high-risk territories for health certificates to establish that they are free of the new coronavirus.

Travellers who cannot provide documentation should be prevented from boarding flights to the Asian nation, according to a Civil Aviation Authority of Thailand notice posted on Monday (March 9). Carriers are liable for treatment costs if they fly in people who become sick with Covid-19, the notice said.

The new framework applies to six territories: China, Hong Kong, Macau, South Korea, Iran and Italy. Thailand has designated them danger zones for infection as it steps up efforts against Covid-19 after so far restricting the number of confirmed cases to 50.

The Tourism Authority of Thailand, a government agency, wrote on Facebook on Monday that travellers coming from the six regions "will undergo 14 days quarantine", adding more details will be announced shortly.

"We advise all travellers to consider carefully whether they still want to pursue their journey," the authority wrote.

The Facebook post follows a series of confusing flip-flops on the matter, which left it unclear whether self-quarantine for those coming from the danger zones is mandatory or only strongly recommended.

A plunge in crude oil prices and escalating fears over the impact of the Covid-19 outbreak sparked a 7 per cent plunge in Thai stocks on Monday, the worst drop since 2014. Tourism-reliant Thailand's economy is reeling from the virus as travellers - especially from disease epicentre China - stay away.