Thailand's Meteorological Department has issued a weather alert for 38 provinces, warning of continuous heavy rain affecting 70 percent of areas with risks of flash floods and overflow. Bangkok and surrounding areas are also included. As of August 21, 2025, the department forecasts heavy to very heavy rain in the northern and upper northeastern regions, with heavy rain in central and eastern Thailand including Bangkok and its vicinity over the next 24 hours.

A monsoon trough is passing through the northern and upper northeastern regions, combined with strong southwest monsoon winds over the Andaman Sea and Gulf of Thailand. Residents in affected areas are urged to be cautious of heavy to very heavy rainfall and accumulated water, which may cause flash flooding, flash floods, and riverbank overflow, especially in foothill and low-lying areas.

Wave heights in the upper Andaman Sea and upper Gulf of Thailand are expected to reach 2-3 meters, exceeding 3 meters during thunderstorms. The lower Andaman Sea will see waves around 2 meters, over 2 meters during thunderstorms. Fishing boats in both areas are advised to navigate carefully and avoid thunderstorm zones, with small boats in the upper regions advised to stay ashore.

For the 24-hour forecast from 6:00 a.m. today to 6:00 a.m. tomorrow:

Northern Region: Thunderstorms in 80 percent of areas with heavy rain in some areas, particularly in Mae Hong Son, Chiang Mai, Chiang Rai, Lampun, Phayao, Nan, and Phrae provinces. Very heavy rain expected in Lampang, Kamphaeng Phet, Uttaradit, Sukhothai, Tak, Phitsanulok, Phichit, and Phetchabun. Minimum temperature 23-26°C, maximum 27-32°C. Southwest wind 10-20 km/h.

Northeastern Region: Thunderstorms in 80 percent of areas with heavy rain in some areas, particularly in Bueng Kan, Sakon Nakhon, Nakhon Phanom, Chaiyaphum, and Khon Kaen. Very heavy rain expected in Loei, Nong Khai, Nong Bua Lamphu, and Udon Thani. Minimum temperature 22-25°C, maximum 26-30°C. Southwest wind 10-20 km/h.

Central Region: Thunderstorms in 70 percent of areas with heavy rain in some areas, particularly in Nakhon Sawan, Uthai Thani, Kanchanaburi, and Ratchaburi. Minimum temperature 23-25°C, maximum 28-33°C. Southwest wind 10-25 km/h.

Eastern Region: Thunderstorms in 70 percent of areas with heavy rain in some areas, particularly in Nakhon Nayok, Prachuap Khiri Khan, Chanthaburi, and Trat. Minimum temperature 23-28°C, maximum 29-33°C. Southwest wind 20-40 km/h. Sea waves 2-3 meters, exceeding 3 meters during thunderstorms.

Southern Region (Eastern Coast): Thunderstorms in 40 percent of areas, mainly in Phetchaburi, Prachuap Khiri Khan, and Chumphon. Minimum temperature 23-26°C, maximum 29-36°C. From Surat Thani northward: Southwest wind 15-35 km/h, waves 1-2 meters nearshore, exceeding 2 meters during thunderstorms. From Nakhon Si Thammarat southward: Southwest wind 15-35 km/h, waves around 1 meter nearshore, 1-2 meters offshore, exceeding 2 meters during thunderstorms.

Chiang Rai—Border Patrol Police at Chiang Saen checkpoint, working with military and local police, have arrested four Chinese men caught illegally crossing the Mekong River into Thailand. Three Thai citizens have also been detained for allegedly helping or sheltering the foreign nationals.

On August 20, 2025, the Chiang Saen immigration investigation unit, led by Panumasc Bunlaksem, commander of the Border Patrol Police, and Sarawut Khonyi, head of Border Patrol Region 5, received intelligence about smuggling attempts across the Mekong River. Officers from the Border Patrol Police, local forces, Chiang Rai Tourist Police, and Chiang Saen Police conducted surveillance along high-risk sections of the riverbank.

At approximately 12:30 p.m., officers spotted suspicious activity near the riverbank at Ban Pa Sak Hang Wiang, Wiang subdistrict, Chiang Saen district. They observed men emerging from the Mekong River and moved in to apprehend them.

Four Chinese nationals were arrested: Jin Yonggang, 24; Di Jinxin, 39; Guo Yuchen, 33; and Zhang Penghan, 34.

Three Thai nationals were also arrested for allegedly assisting or harboring the foreign nationals: Phutthachat, 53; Ratnaporn, 27; and Chetsada, 22.

All suspects have been handed over to Chiang Saen Police for legal proceedings. Investigators are expanding their inquiry to identify additional routes and individuals involved in the smuggling operation.

Mae Hong Son — Flash floods have swept through the renowned Karen Long Neck tourist village of Huay Sua Thao in Pha Bong subdistrict, Mueang district, Mae Hong Son province. The raging stream destroyed the souvenir shop zone, washing away merchandise, and swept away a wooden bridge that connects the community to the outside world. Residents have been cut off from the outside.

On August 20, 2025, heavy rainfall throughout Mueang district triggered flash floods, sudden inundation, and mudslides across multiple villages. The Huay Sua Thao area was particularly hard hit, with the swollen stream flowing violently through the center of the village. The souvenir shop zone suffered severe damage, with large quantities of goods swept away by the floodwaters.

The wooden bridge spanning the stream at the center of Huay Sua Thao, which connects the Karen community to the outside, was destroyed by the floods.

During the incident, Karen residents living near the waterway evacuated and moved to higher ground. Many houses in Huay Sua Thao located near the stream and along the village entrance road were flooded.

Community leaders, along with senior officials, administrative staff, local government representatives, Mae Hong Son Provincial Organization volunteers, the Pha Bong Subdistrict Administrative Organization, and related agencies, deployed to the area to assess the situation and provide urgent assistance to residents. They are working to evaluate damage and restore access routes as quickly as possible.

Authorities urged residents to exercise caution during travel due to ongoing strong currents and to stay in close contact with local officials.

Immigration authorities in Surat Thani province, working with investigative units and related agencies, conducted an enforcement operation against illegal foreign workers on Koh Tao in Koh Phangan district on August 20. Officers raided four locations: two dive companies, one pharmacy, and one beauty salon, arresting foreign nationals ranging from dive instructors to workers taking jobs reserved for Thai citizens.

The operation followed directives from senior police officials. Immigration officers found six foreign nationals working as unlicensed dive instructors, including one British man identified as Adam and five Spanish nationals: Xabier, Pablo, Paulina, Sandra, and Nuria. All were using DTV (digital nomad) visas but illegally took positions teaching diving. Authorities are investigating company executives and examining financial records for possible nominee involvement.

At a pharmacy, officers arrested a Myanmar national, Cha Chi Lin, for selling herbal medicines without pharmacist supervision in violation of work permit conditions. At a beauty salon on Sai Ree Beach, two Myanmar women, Sin Sin Miao and Tin Tin Wei, were arrested for performing nail services—work restricted to Thai nationals—despite their permits authorizing only general labor. All suspects were transferred to Koh Tao police for legal proceedings. Statistics show 47 foreign nationals arrested for labor violations in Koh Tao from January through August 2025 under various laws including the Alien Occupation Act, Immigration Act, and narcotics laws.

A fisherman in Prachuap Khiri Khan received the shock of his life when he discovered an unidentified male corpse floating face-down and bloated beneath a bridge over the Bang Pakong River in Kabinburi Sub-district, Prachuap Khiri Khan Province. Police investigator Hasaworn Panjamhat and hospital emergency staff rushed to the scene and recovered the body. The deceased was a man estimated to be 35–40 years old, wearing a short-sleeved shirt and shorts, and appears to have been dead for at least two days. The body bore tattoos and showed mysterious bruising across the body, especially under the chin, which preliminary medical examination could not immediately explain. No identification documents were found on the body. Witness Kittisak Sribuppha, who discovered the corpse while fishing with friends, described his shock when he spotted the body drifting toward them after a passing boat drew near the bridge pier. Police have ordered rescue personnel to conduct a detailed autopsy to determine the true cause of death—whether accidental drowning or something else—and to identify the victim and contact relatives.