The Centre for Covid-19 Situation Administration (CCSA) is concerned that many Thais are expected to travel to their provincial homes during the long holiday on July 4-7, which could lead to a new surge in Covid-19 infections, spokesman Taweesilp Visanuyothin said.

After the fifth phase of easing of Covid-19 restrictions started on Wednesday, authorities at the centre anticipate that Thais will return in large numbers to their home provinces during the Asarnha Bucha and the Buddhist Lent Day period.

"When they return home, they will gather with friends for drinking. It is their way of life," Dr Taweesilp said.

He said disease monitoring in local areas is efficient with village health volunteers working to prevent the spread of the disease from returnees to elderly members of their families.

However, illegal migrant workers have continued to sneak across borders, Dr Taweesilp said.

"So we cannot feel 100% at ease. It was reported last month that more than 2,900 illegal workers crossed the border and stayed with us," he said.

He said Thais must continue to comply with health safety measures to protect themselves from the disease by maintaining physical distancing and wearing face masks.

"Thailand has survived the past six months because of cooperation from everyone," Dr Taweesilp said.

Among premises allowed to reopen from Wednesday were pubs and bars, karaoke bars, and bath-sauna-massage establishments - effectively brothels.