Flash floods and mudslides across Thailand brought by monsoon rains have killed 22 people and injured 19, authorities said on Monday, warning some provinces of further risk, with 30,000 households affected.

A Russian couple and nine migrant workers from neighbouring Myanmar were among 13 people killed in a mudslide on the southern island of Phuket, officials said after the rain lashed a dozen provinces last week.

Prime Minister Paetongtarn Shinawatra handed out food supplies to people during weekend visits to their homes in the northern area of Nan.

Rescuers were battling to pull three workers from debris after a tunnel collapsed at a Thai-China railway construction project in the northeastern province of Nakhon Ratchasima, the transport ministry said.

Severe flooding persists in five northern provinces, such as Chiang Rai, Sukhothai and Prae, while there is a high risk of waters rising in areas near the Chao Phraya River, including the capital, Bangkok, though levels are still manageable.