BANGKOK (BLOOMBERG) - Thailand is rushing to vaccinate its elderly citizens and other vulnerable groups ahead of the local New Year celebrations as the festivities could fuel a surge in Covid-19 cases and deaths, potentially derailing a tentative economic and tourism recovery.

Millions of Thais will travel to their home towns this week from cities such as Bangkok to join families in celebrating Songkran, the first time they can do so without any travel curbs since the outbreak of the pandemic.

This has prompted the Health Ministry to warn on Monday (April 11) that new daily cases could jump to as high as 100,000 a day from around 20,000.

A booster-dose campaign for the elderly had seen an estimated 500,000 people getting vaccinated in the past three weeks, taking the total number of those aged above 60 with three shots to three million.

But there is a long way to close the gap as the South-east Asian nation has an estimated 11 million senior citizens, Health Ministry data shows.

With only about 35 per cent of the 70 million Thai population receiving booster shots, Prime Minister Prayut Chan-o-cha on Monday urged people to adhere to Covid-19 protocols to prevent a spike in cases after the long holidays.

This is key to the tourism-reliant nation's efforts to further relax visa rules for foreign visitors.

"There will be a lot of parties and meetings during Songkran and we expect there will be a lot more infections," Health Minister Anutin Charnvirakul said last week. "But vaccines can help reduce the risk and we are asking people to cooperate, so the nation can get over this risky period."

A flare-up in infections could potentially bring back more restrictions and scuttle a fragile economic recovery that is already facing headwinds triggered by the Russian invasion of Ukraine.

Most economists have trimmed Thai growth forecasts in recent weeks while predicting a second straight year of current account deficit on a bleak outlook for a recovery in tourist arrivals.

"We are concerned about a sharp rise in new infections after Songkran," said economist Nattaporn Triratanasirikul at Kasikornbank's research unit.

"The higher the cases, the longer it will take for the outbreak to stabilise and delay the plan to declare it as endemic. But the impact will be less than the forced lockdowns we faced in the previous years."

Even if new cases flare up, the nation's healthcare system will still be able to cope as the high rate of vaccination will prevent severe infections and the need for hospitalisation, according to Dr Chakkarat Pittayawonganon, director of the Bureau of Epidemiology. The bureau expects cases to stabilise in May.

Mr Prayut's government, which has followed a strategy of living with Covid-19 since October last year by gradually ending most of the mobility restrictions, is seeking a balance between public health and the economy.

It aims to declare the outbreak endemic by July if it can keep daily new infections to a few thousand and fatalities below 80 a day.