On August 20, the Thai Meteorological Department forecast heavy rain in scattered areas across Thailand over the next 24 hours, with very heavy rainfall expected in parts of the North, Northeast, Central, and Eastern regions. A monsoon trough is passing through the upper North and upper Northeast, moving into a strong low-pressure system near Hainan Island in China, combined with a moderately strong southwest monsoon over the Andaman Sea and Gulf of Thailand.

Residents in affected areas are warned to watch for dangers from heavy to very heavy rainfall and accumulated precipitation, which may cause flash floods, overflowing streams, and riverbank overflow, particularly in foothill areas near water channels and low-lying zones. In the Andaman Sea's upper section and upper Gulf of Thailand, wave heights reach 2–3 meters, exceeding 3 meters during thunderstorms. In the lower Andaman Sea, waves are approximately 2 meters, exceeding 2 meters during thunderstorms. Boat operators are urged to navigate cautiously, avoid thunderstorm areas, and small boats in the upper Andaman should remain ashore.

The North will see thunderstorms in 80 percent of areas with heavy rain across Chiang Mai, Chiang Rai, Lampun, Lamphun, Phayao, Nan, Phrae, and Kamphaeng Phet, with very heavy rain in Mae Hong Son, Uttaradit, Sukhothai, Tak, Phichit, and Phetchabun. Temperatures range from 22–27 degrees Celsius minimum to 27–31 degrees maximum, with southwest winds at 10–20 kilometers per hour.

The Northeast will experience thunderstorms in 80 percent of areas with heavy rain across Nong Khai, Nong Bua Lamphu, Udon Thani, Chaiyaphum, Khon Kaen, Kalasin, Mukdahan, Maha Sarakham, Roi Et, Yasothon, Amnat Charoen, Nakhon Ratchasima, and Ubon Ratchathani, with very heavy rain in Loei, Bueng Kan, Sakon Nakhon, and Nakhon Phanom. Temperatures range from 22–25 degrees minimum to 26–32 degrees maximum, with southwest winds at 10–20 kilometers per hour.

The Central Region will see thunderstorms in 70 percent of areas with heavy to very heavy rainfall in Nakhon Sawan, Uthai Thani, Chai Nat, Lopburi, Saraburi, Kanchanaburi, Ratchaburi, Nakhon Pathom, Samut Sakhon, and Samut Songkhram. Temperatures range from 23–26 degrees minimum to 29–33 degrees maximum, with southwest winds at 10–25 kilometers per hour.

The East will have thunderstorms in 70 percent of areas with heavy rainfall in Nakhon Nayok, Prachuap Khiri Khan, Sa Kaew, and Chanthaburi, and very heavy rain in Trat. Temperatures range from 23–28 degrees minimum to 30–33 degrees maximum, with southwest winds at 20–40 kilometers per hour. Sea waves are 2–3 meters high, exceeding 3 meters during thunderstorms.

The South's eastern coast will see thunderstorms in 40 percent of areas with heavy rain in Phetchaburi and Prachuap Khiri Khan. Temperatures range from 23–27 degrees minimum to 32–36 degrees maximum.

Natural Resources and Environment Minister Suchart Chomklin has instructed the Pollution Control Department to closely monitor waste disposal sites and wastewater treatment systems in flood-prone areas of Nan province to prevent environmental and public health impacts. Heavy rainfall, flash floods, and flash-flood currents could disrupt wastewater systems or wash garbage into water sources, causing contamination.

According to Surin Vorakitdharm, director-general of the Pollution Control Department, the Lamphun Environmental and Pollution Control Office found that the Tha Wang Pha Municipal Subdistrict waste disposal site covers 100 rai and handles approximately 4.78 tonnes of waste daily. The Nan City Municipal waste disposal site covers 60 rai and processes about 80 tonnes per day from 21 local administrative organizations, using proper sanitary landfill and MBT (integrated community waste management) systems, neither currently affected by flooding.

The Nan City Municipal wastewater treatment system, which handles 8,259 cubic metres daily with four pumping stations and 16 sump tanks covering approximately 90 percent of the service area, has also not been affected. The Lamphun office has coordinated with local agencies to monitor waste collection and storage in flooded areas according to scientific standards, prevent garbage from being swept into communities and water sources, and address leachate, odour, and sanitation concerns. The Pollution Control Department will monitor the situation closely and take immediate action if impacts are detected, and has urged the public and local agencies to report any problems by calling 1650.

Songkhla—The Hope animal welfare organization, working with public health officials from Songkhla Municipality and the prevention and suppression division of Songkhla City Police, has rescued a two-year-old female Siberian Husky named Polly who was abandoned in a house alone for three months. Neighbors fed and watered her through the fence out of compassion, while at night the distressed dog cried out in loneliness.

After officials met with the dog's owner and father, they agreed to surrender Polly to the animal welfare organization for health care, vaccinations, and spaying. Polly has since been bathed and had severely matted fur removed. Now approximately two years old, she is cheerful and playful, but given her high energy levels and characteristic Siberian Husky temperament, the organization is looking for a prepared and committed home.

Requirements for potential adopters include adequate space and time to care for a high-energy dog, experience with Siberian Huskies or Huskies, and willingness to allow staff to conduct home inspections and follow-up visits. Those interested in adopting Polly can contact The Hope Songkhla at 089-737-7917.

On August 19, 2025, police announced results of a large-scale anti-drug operation targeting a major trafficking network. Acting on an investigation that began with the arrest of a suspect carrying 105 grams of crystal methamphetamine in the Ramkhamhaeng area in late July, detectives identified a criminal group smuggling drugs from northeastern Thailand into Bangkok and its suburbs.

Undercover officers arranged to purchase 200,000 methamphetamine pills, leading to a sting operation on August 16 in Pathum Thani province. At around 7:20 p.m., Wattana, 39, arrived in a black Toyota Fortuner with two suitcases containing drugs to hand over to an undercover agent. Police moved in to arrest him and three associates waiting at a Big C shopping mall: Arisa, 53; Thawi, 48; and Vishnu, 35.

Following the arrests, officers searched Vishnu's residence in Lad Lum Kaew district, Pathum Thani, which served as a drug hideout. The search uncovered 1,826,000 additional methamphetamine pills and components for 14 firearms, 13 magazines, four gun barrels, and ammunition. In total, police arrested four suspects, seized 2,036,000 pills, two vehicles, and five mobile phones. Officers also seized assets believed to be proceeds of crime, including two land titles, three bank books, a car, and a motorcycle, valued at over 63 million baht. The suspects face charges of drug trafficking and weapons violations.

Deputy Prime Minister Yotchanan Wongswatsdi and Agriculture Minister Suriya Juangrungkit, together with Deputy Interior Minister Jachai Thai-sahat, visited the N.1 water-monitoring station near Nan city on August 19 to oversee the escalating flood situation. The visit was attended by senior officials from the Irrigation Department and provincial administrators.

Extreme rainfall concentrated in Pua District has caused severe flooding across four districts: Pua, Phu Phiang, Santisukhon, and Tha Wang Pha, with water levels ranging from 50cm to 1.2 metres. The Nan, Pua, Yang, and Khwang rivers have all overflowed, threatening homes and agricultural land.

Minister Suriya ordered 24-hour monitoring and mobilized water pumps—including a 14-inch pump in Muang Nan and three 8-inch pumps in Wiengsa—to accelerate drainage and relief efforts. Current water levels at the N.1 station stand at 7.62 metres, approximately 88cm below the reinforced embankment, but are rising steadily. Officials warn water may breach defenses by 60cm in Muang Nan District between 2:00 and 4:00 on August 20.

Deputy PM Yotchanan announced a unified single-command emergency center operating around the clock, with cabinet approval and full provincial coordination. Residents in high-risk areas are urged to evacuate to safe zones immediately and move valuables at least 60cm high. Emergency alerts have been broadcast via cell phones. The Interior Ministry is preparing rehabilitation plans for affected communities once water levels recede.