Southeast Asia is one of the fastest growing regions in the world. Rising demand and increasing economic activity have led to steady progress in the development of high-capacity transport infrastructure. Countries across the region are increasingly turning to mega projects such as expressways, tunnels and large-scale bridges to ease road congestion, strengthen urban mobility and expand regional connectivity. The overall objective of these initiatives is to reduce travel times and unlock economic growth opportunities.
Thailand is no exception to this trend. The country unveiled the Rama X Bridge in January 2025 in Bangkok, a landmark cable-stayed structure and the widest river bridge in the country. Spanning across the Chao Phraya river, the bridge has been designed as a strategic addition to the city’s expressway network. The project aims to ease traffic flow between Bangkok and its western and eastern suburbs, offering alternative routes to commuters for river crossing. The project stands as an engineering marvel, highlighting Thailand’s ability to deliver world-class infrastructure.
Building the new link
The Rama X Bridge, officially named Saphan Thotsamarachan, was opened for vehicular traffic on January 29, 2025. The eight-lane cable-stayed bridge spans 780 metres across the Chao Phraya river, with a total length of about 2 km, making it the widest river crossing in Thailand. The bridge connects Bangkok with Suksawat Road and the western ring road in Thon Buri, and is intended to ease congestion on Rama II Road and the Chalerm Maha Nakhon Expressway. The project is designed to carry an estimated 150,000 vehicles per day. It will reduce traffic on Rama II Road from about 100,000 to 75,000 vehicles daily. The project was implemented by the Expressway Authority of Thailand (EXAT), which will continue to oversee the operations of the project. The main contractor for the project was CH. Karnchang Public Limited, which undertook the project in 2019.
The bridge forms a key component of the Rama III-Dao Khanong-Bangkok Outer Ring Road Expressway (western section), an 18.7 km elevated corridor currently under construction. Once complete, this expressway will serve as the primary route linking Bangkok with the country’s western and southern regions, strengthening connectivity and supporting long-term economic growth.
Bangkok’s new architectural marvel runs parallel to the old Rama IX Bridge, offering an alternative route with eight traffic lanes. Rama IX Bridge will undergo a year-long maintenance upgrade, including installation of modern sensor systems for enhanced safety. This maintenance work will mark the first substantial refurbishment the bridge will undergo after over 30 years. The year-long service aims to keep it operational for many more years to come. The Rama IX Bridge became operational in 1987; since then, it has remained a vital river crossing for over three decades. The bridge will continue to act as a backup link and historical symbol of the country’s infrastructure once maintenance is completed. Moreover, with two operational bridges, the overall network incident response capability will significantly improve.
Funding the mega structure
The Rama X Bridge has been financed as part of the elevated expressway corridor, which has been structured into five civil contract packages with a total investment of THB 29.3 billion. Of this, around THB 6.6 billion was allocated for the bridge contract. The funding has been secured entirely through the Thailand Future Fund (TFF), with no direct budgetary allocation. Under this framework, future toll revenues are securitised to raise upfront capital, while revenues are ring-fenced for debt servicing and long-term maintenance. For users, toll fees on the expressway section encompassing the new bridge have been set at THB 50 for four-wheel vehicles, THB 75 for six- to ten-wheel vehicles, and THB 110 for vehicles with more than 10 wheels.
Engineering and design leaps
The new bridge has a central span that reaches an impressive 450 metres, carried by two H-shaped pylons anchored with 152 stay cables. The longest stay cable has a length of 233.7 metres. The bridge has been built to withstand wind speeds of up to 270 km per hour and is seismic resilient, ensuring safety even during severe weather conditions and earthquakes. Being the widest bridge of its kind in Thailand, the Rama X Bridge required exceptionally long expansion joints in its superstructure. To address this, about 68 metres of modular expansion joints with a cantilever design and a movement capacity of 400 mm were incorporated. These allow the deck to accommodate thermal expansion and contraction, ensuring smooth driving comfort and preventing structural distress over its lifetime.
In addition, more than 1,100 high-capacity pot bearings were installed to support the superstructure of the expressway’s long viaduct leading to the bridge. Among these, 58 bearings were specifically engineered to resist uplift forces, a critical safety requirement in a long-span cable-stayed structure. The largest bearings are capable of sustaining vertical loads of up to 12,750 kilonewtons (kN), enabling the bridge to safely distribute enormous forces from traffic and structural loads on its foundations.
The new bridge is not only modern in its technical design, it also incorporates impressive structural features and symbolic elements that reflect Thailand’s heritage. Four pillars of the bridge have been decorated with golden-yellow naga sculptures, while the bridge fences display decorative patterns inspired by the yellow starflower. These aesthetic choices highlight the bridge’s dual significance as both a modern engineering marvel and a cultural landmark.
In sum
The completion of the Rama X Bridge marks a defining step in Bangkok’s infrastructure journey. Beyond being a new river crossing, it is a strategic investment in the city’s long-term growth and highlights Thailand’s capacity to deliver world-class projects. By expanding capacity and offering an alternative alongside the Rama IX Bridge, it strengthens the resilience of the capital’s transport network.
While its scale and technical features reflect advanced engineering, the bridge also carries national significance, blending modern design with cultural aspects. More importantly, it represents a forward-l
Looking approach, easing congestion today while positioning Bangkok for sustainable growth tomorrow. It not only supports the daily mobility of residents and the efficiency of freight operations but also stands as a landmark achievement in Thailand’s commitment to building infrastructure that supports the scale and pace of its growing economy.
