The tragedy is the latest in the country's ongoing severe flooding covering massive areas of the North, Northeast and Central regions with no sign of letup.
The death toll from the flooding reached 112 on Monday and two still missing.
It took a team of divers five hours to retrieve the bodies of the drowned man and his daughters, aged 11 and nine. The father and his children were collecting dead fish in the river when the boat tipped over in the strong current.
The man tried to save his daughters who held on to him tightly, but all three were pulled down into the rushing water, according to media reports.
The flood situation in a number of provinces remains critical.
In Ubon Ratchathani, the water level in the Mool River rose to 2.19 metres, while the overflowing Mekong River put the provincial centre under water. The river continues to rise by 10 centimetres a day, forcing local residents to shelter along higher roads. Health and hygiene are problems as there are insufficient mobile toilets.
Meanwhile, provincial authorities in Maha Sarakam province declared two additional districts disaster zones bringing the number of critically affected districts to six. More than 34,000 rai of crops have been damaged or destroyed.
In Ang Thong, water from the Chao Phraya River flowed into the Noi River, deluging houses along the river and affecting residents. Water flowed into Wisetchaichan Tantiwitayaphum School and with floodwater 60cm deep enveloping its buildings, the school was closed for a week for safety reasons.
In Nan, a crevasse one metre wide and an estimated 100 metres long, was found in a mountain ridge area in Phu Phiang district. Local residents were warned of a possible landslide and to be on high alert for possible evacuation.
In its latest warning issued on Monday, the Meteorological Department warned that heavy rains would continue in the North and Northeast.
A moderate high pressure ridge from China will extend into upper Thailand causing a monsoon trough over neighbouring Burma and upper Laos moving across to the North and upper Northeast Thailand.
The weather service said the monsoon trough is expected to lie across Thailand's central and lower northeastern regions from Tuesday through Friday, while the southwest monsoon over the Andaman Sea, the South and the Gulf of Thailand will intensify.
In other developments, Army chief Gen Prayuth Chanocha led senior officers from the Military Engineers Department to visit flood victims in hard-hit Uttaradit province. He instructed his subordinates to work with concerned agencies to help rebuild and rehabilitate the area.