* Sees 2022 GDP growth at 3.9% vs 3.6% projected earlier

* Says Omicron coronavirus variant a risk

* Forecasts policy rate still unchanged at 0.5% next year

BANGKOK, Dec 14 (Reuters) - Thailand's economy is still expected to grow 1% this year due to the impact of a coronavirus outbreak, but growth is expected to accelerate to 3.9% next year, driven by a recovery in service sector activity, the World Bank said on Tuesday.

Southeast Asia's second-biggest economy shrank 6.1% last year, with the vital tourism sector still struggling. Thailand reopened https://www.reuters.com/business/aerospace-defense/bangkok-welcomes-first-tourists-quarantine-free-holiday-2021-11-01 more broadly to vaccinated foreign visitors in November and eased https://www.reuters.com/article/idUSL1N2Q006L strict curbs as new infections decline.

"A major surge in COVID-19 cases severely slowed economic activity in Thailand during Q3 of 2021, but a recovery is now underway," the World Bank said in its latest Thailand Economic Monitor.

Economic activity is expected to return to pre-pandemic levels by the end of 2022, with vaccinations and a resumption of tourist arrivals providing support, it said.

While the number of foreign tourists is likely to be negligible this year, it is projected to rise to almost 7 million in 2022 and to around 20 million in 2023 - albeit still half of the 2019 level, the World Bank said.

In late September, it forecast only 1.7 million foreign tourists next year with economic growth of 3.6%.

Growth risks, however, are skewed to the downside due to uncertain variables, the World Bank said.

The new Omicron variant is one such risk and if there were new containment measures and border closures, the economy could contract 0.3% in 2022, Kiatipong Ariyapruchya, senior World Bank economist for Thailand, told a briefing.

Thailand said it would expedite COVID-19 boosters in anticipation of a local spread of Omicron.

Monetary policy is expected to remain accommodative to support the recovery, with the policy interest rate https://www.reuters.com/article/idUSL4N2S019V still seen unchanged at a record low of 0.50% in 2022, the World Bank said. It said Thailand, with its strong external position, was relatively less exposed to policy normalisation by the United States. (Additional reporting by Satawasin Staporncharnchai Editing by Ed Davies)