Three people drowned on Saturday as 12 provinces were put on alert for floods as Tropical Storm Dianmu battered northern Thailand.

Going, going, gone: A bridge in Ban Mae Suk in tambon Wangsai of Lampang's Wang Nua district collapses into the Wang River amid ferocious torrents. Video credit: YouTube user คลิปเด็ด Hot Clips

The Northern Meteorological Centre warned that more heavy rain is expected in Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Nan, Phrae, Lamphun, Lampang, Uttaradit and Tak. Phichit and Sukhothai were already feeling the force of the waters on Saturday.

Residents were warned of possible flash floods and forest runoffs due to torrential rain.

Three villagers died in flooding in Chiang Rai on Saturday. They were identified as Chan Yuenyongsaen, 80, from Mae Chan district, Thep Saengkaew, 58, from Mae Suai district, and Boonruang Phumthawong, from Muang district.

In nearby Chiang Mai, a heavy storm hit parts of Mae Ai district and destroyed 34 houses in three villages.

Heavy rain was reported in widespread areas of Chiang Mai yesterday. Scores of trees fell and blocked roads in tambon Pingkong of Chiang Dao district, causing a traffic jam.

In Lampang, two bridges across the Wang River in tambon Wangsai of Wang Nua district collapsed under intense runoff from Doi Luang National Park.

Authorities have warned Phichit residents to brace for possible floods as a large volume of water in the Yom River heads downstream towards the province.

Somyot Sangmanee, chief of Phichit Provincial Irrigation Office, said yesterday the Yom River was flowing to Phichit from Phitsanulok's Bang Rakam district at a rate of 200 cubic metres per second, raising the river by 15cm, though it was still three or four metres lower than the riverbank.

Sluice gates at a canal in tambon Kampangdin of Sam Ngam district of Phichit have been raised to push water from the Yom River to the Nan River in Bang Krathum district of Phitsanulok to ward off potential flooding in Phichit.

Residents have been urged to get prepared and keep monitoring information about the water situation from authorities and the media, Mr Somyot said.

Leaders of communities in the province were urged to warn residents to move their belongings to higher ground, Phichit governor Chatporn Rajdussadee said, adding she believes the situation will be under control.

The governor was speaking as she and Mr Somyot surveyed the Yom River at a temple in tambon Rangnok of Sam Ngam district.

Teerapong Petpong, chief of the Rangnok tambon administration organisation, said his supervised area is normally prone to flooding as it is close to the Yom River.

With raised houses and boats, the locals are not worried about overflows, he said.

In Phitsanulok, north of Phichit, the old route of Yom River rose by 1.2m in Phrom Phiram district, said Chamnan Chuthiang, chief of the Yom Nan Water Transmission and Maintenance Project.

Local leaders surveyed the flood-risk areas and ordered the reinforcement of the embankment.

However, the river and its associated canals started to burst their banks in tambon Tha Chang of Phrom Phiram district, prompting residents to move their belongings to higher ground and scramble to plug pipes that carry water to rice fields.

In Sukhothai, the Regional Irrigation Office 4 reported yesterday that the Yom River passing through the province was now manageable as the level of the river had dwindled. The office still warned residents to still keep monitoring the news as Dianmu was dumping rain in Phrae and Phayao provinces.

Prime Minister Prayut Chan-o-cha has praised Sukhothai governor Piti Kaewsalapsi for leading efforts to successfully prevent flooding in the province, according to government spokesman Sansern Kaewkamnerd.

Local authorities erected big bags to defend the overflows and succeeded in funnelling water into natural water catchments, which helps lower the river to a manageable level, Maj Gen Sansern said.

"The prime minister wants other provinces to use Sukhothai as an example to learn how to deal with water problems, particularly the integrated efforts by all sectors to deal with the situation in the areas," said Maj Gen Sansern, adding the provincial governor plays a leading role in handling the situation.

In Lampang, sluice gates at a weir in Wang Nua district were opened to allow the quick flow of water and get ready to cope with new runoff.

Kreangsak Saengyunon, Wang Nua district chief, said authorities remain vigilant over possible flooding. Villagers in eight tambons near the Wang River have been warned to be alert to the situation, he said.

Downpours were reported throughout Nan. Forest runoff hit tambon Silapet of Pua district, causing damage to houses and farmlands.