Ms Yingluck flew to Ayutthaya, Nakhon Sawan, Sukhothai and Phisanulok.
Flooding in Sukhothai was caused by an eroded flood embankment coupled with a large amount of rainfall but the situation is now under control, she said.
Minister of Natural Resources and Environment Preecha Rengsomboonsuk reported to the premier about the flooding in Sukhothai that the gap in the base of the eroded flood wall is being plugged and the work is almost completed.
Pumps are operating around the clock to drain out floodwater, which is now dropping at a rate of 20 centimetres per hour.
The situation is expected to return to normal within two days.
Ms Yingluck said after the trip today, she could affirm that the water levels in canals and rivers were still manageable as the amount of water is lower than last year. She expressed confidence that the government can handle flood better than last year.
Regarding rehabilitation, she said the same criteria will be applied to compensate flood victims as last year but the process will be sped up following a clarified understanding of the problem and the response.
The premier said she assigned the disaster response agency to keep watch at other locations to prevent a failed embankment from occurring in other areas.