Flooding across Bangkok and 26 other provinces could cost Thailand 12.283 billion baht in lost economic activity between September 25 and 29, 2026, according to the University of the Thai Chamber of Commerce (UTCC). The estimate covers affected areas in the Central, Eastern, Northern and Northeastern regions.
UTCC president Thanavath Phonvichai, who chairs the advisory board of its Center for Economic and Business Forecasting, said the base-case estimate equals 0.066% of annual gross domestic product (GDP).
Depending on the severity and duration of the floods, five-day losses could range from 5.896 billion to 20.635 billion baht, or 0.03% to 0.11% of annual GDP.
The figures cover disrupted economic activity but exclude damage to homes, vehicles, business inventories and agricultural production. Those losses cannot be assessed fully until floodwaters recede and surveys are carried out.
The forecasting centre expects flooding to ease within about a week. It will revise its estimates if the disruption continues longer than expected.
Bangkok Accounts for Most Projected Losses
Bangkok is expected to bear 7.014 billion baht in losses, or 57% of the base-case total. Trade and services in the capital have been affected as flooding makes it harder for customers and employees to travel.
The worst flooding in Bangkok has been concentrated in eastern districts. Disruption to financial firms and office-based businesses has been partly limited by employees’ ability to work from home.
Four neighbouring provinces face combined losses of about 1.839 billion baht, with Samut Prakan the hardest hit, according to the assessment.
In the Eastern region, projected losses total 2.976 billion baht. Chon Buri accounts for 2.101 billion baht after flooding reached the province earlier than other areas, disrupting tourism, retail and port-related logistics.
Thanavath said flooding in other parts of the Eastern Economic Corridor remained localised. No industrial estate in the corridor had been reported to have suspended production.
The centre assessed losses in the Central, Northern and Northeastern regions as relatively limited during the five-day period.
Consumer spending, tourism and urban services have experienced the greatest disruption. Flooding has reduced visits to shopping centres, shops, restaurants and petrol stations, while leaving some employees unable to get to work.
The assessment also counts working days lost during two special public holidays for government offices in Bangkok, Nonthaburi, Pathum Thani and Samut Prakan. Together, those areas generate nearly half of Thailand’s economic output.
In Pattaya and elsewhere in Chon Buri, standing water has led some tourists to cancel or defer trips, cutting revenue for hotels, restaurants and related businesses. Much of the income lost by daily wage workers and small operators may not be recovered.
Flooded main roads have delayed deliveries to some retail branches. Manufacturers have mainly faced difficulties moving staff and raw materials, rather than direct damage to factories, a distinction the assessment drew from the widespread flooding in 2011.
Thanavath said prices of fresh vegetables, especially tender leafy varieties, had started to increase. The centre expects any broader effect on inflation to be temporary and limited, but said prices should be watched during the Vegetarian Festival from October 10 to 18.
Agricultural losses remain a concern in the Chao Phraya basin, including Chai Nat, Sing Buri, Suphan Buri and Phra Nakhon Si Ayutthaya. Water levels are still rising as wet-season rice nears harvest, and crop damage will need to be measured after the floods subside.
At the current estimated scale, the floods are unlikely to alter Thailand’s full-year economic outlook, the centre said. They could, however, weigh on growth in the second half of 2026 if flooding in the Chao Phraya basin extends into the fourth quarter.
“The centre estimates base-case losses of about 12.283 billion baht, equivalent to roughly 0.06% of annual GDP or about 0.26% of GDP in the third quarter of 2026. This comes as Thailand’s economy is slowing, with GDP growth easing to 1.9% in the second quarter from 2.8% in the first,” Thanavath said.
The centre called on the government to provide targeted relief for informal workers and small businesses, offer debt repayment moratoriums or recovery loans, and improve water management in the Chao Phraya basin to protect farms and industrial estates.
It also urged officials to monitor essential goods during the Vegetarian Festival and speed up investment in Bangkok’s drainage system.
