“Phiphat Ratchakitprakarn” explained that the collapse of the Doi Luang tunnel wall in the double-track railway project from Den Chai to Chiang Rai to Chiang Khong was initially attributed to continuous heavy rainfall causing soil saturation and sliding. He emphasized that the entire tunnel has not collapsed and the main structure remains unaffected. A fact-finding committee has been appointed, despite the contractor company's connections to government figures, with results expected within 15 days.
Deputy Prime Minister and Minister of Transport Phiphat Ratchakitprakarn addressed the wall collapse of the Doi Luang tunnel in the Den Chai–Chiang Rai–Chiang Khong double-track railway construction site. Initial reports indicate the incident relates to natural factors, specifically continuous heavy rain saturating the soil and causing sliding. However, it is not a full tunnel collapse but a failure of the wall in the construction area. The Ministry of Transport prioritizes safety in all infrastructure projects but acknowledges that some natural events, like heavy rain or geological changes, can be difficult to predict or fully prevent.
"When heavy rain causes the soil to saturate, sliding can occur. Sometimes this is hard to prevent due to the extensive and complex nature of construction sites. Nevertheless, I believe engineers, contractors, and supervisors have made every effort to manage and prevent such incidents. Accidents in construction can happen despite strict safety measures. This does not mean the government or contractors shirk responsibility, but some events may exceed the assessed risks and preventative measures," Phiphat said.
Phiphat added that all Ministry of Transport construction projects have quality control systems based on international standards, including ISO, which clearly define procedures from start to finish. Engineers, contractors, and project owners, such as the State Railway of Thailand (SRT), strictly follow these procedures. After the incident, the Ministry has ordered all involved agencies to enhance oversight and monitoring of construction work to prevent recurrence.
Regarding public concerns about the contractor company linked to some political figures—comprising the joint venture of Sino-Thai Engineering and Construction Public Company Limited, Ch. Karnchang Public Company Limited, and Chiang Mai Construction Company Limited—Phiphat said personal relationships should not be an issue. The focus should be on the qualifications and capability of companies bidding. Whether a company is related to anyone should not affect eligibility; if a company meets the criteria, it is entitled to compete and win contracts like any other.
He added that the contractor selection process now involves experts and engineering institutions as advisors at several stages to ensure thoroughness and transparency. Procurement follows government regulations, with relevant authorities overseeing legal compliance. A fact-finding committee will definitely be established to determine whether the incident was a natural disaster, an accident, or due to negligence by any party.
The investigation is expected to take some time since engineering experts must conduct an in-depth examination to officially analyze and conclude the facts. Regarding assistance and initial compensation for affected parties, contractors are responsible under contract terms, including insurance related to accidents. Meanwhile, the State Railway of Thailand will discuss further care and support measures.
Phiphat stated that no contractors have been blacklisted or disqualified from bidding at this time, pending investigation results. He emphasized the Ministry will not grant exemptions or special privileges to any company. All companies are treated equally in public bidding, requiring readiness and expertise per set criteria. There is no discrimination based on ownership or affiliations; all are equal contractual partners with the Ministry of Transport.
. Deputy Minister of Transport Siripong Angkasakulkiat said that recently, Chiang Rai province has experienced continuous heavy rainfall, causing soil saturation. This resulted in pressure and some soil sliding into the tunnel, covering about 5 square meters. Engineers and supervisors are closely monitoring the situation and have increased surveillance measures, adding support systems to enhance safety.
The Ministry of Transport is taking the incident very seriously. Currently, Deputy Minister of Transport Phattharaphong Phattharaprasit, who oversees the northern zone, along with relevant officials, have visited the site to monitor the situation. They have not ruled out other possible causes such as negligence or other factors. A thorough fact-finding investigation will be conducted to reach a clear conclusion. Initial data suggests the primary cause is likely heavy rain and water accumulation in the soil, but authorities continue to investigate the true cause.
Siripong assured that the public need not worry about the overall tunnel structure as only the initial structural layer was affected. The tunnel is still under construction and requires additional concrete layers and structural work—two to three layers more—before completion to engineering standards.
"Currently, the tunnel is only at the first construction layer after excavation. It has not yet entered the process of final surface sealing or complete structural sealing, including waterproofing systems. Therefore, during prolonged heavy rain, moisture and water from the soil can still penetrate the construction area," Siripong explained.
He noted that tunnels normally have drainage and groundwater management systems, but because construction is ongoing and rainfall has been unusually heavy for the season, accumulated water burden exceeded normal levels. Although the structure is designed to handle such loads, incomplete construction stages allowed this incident to occur.
Siripong said the Prime Minister has instructed all involved agencies to intensify supervision of large-scale construction projects, especially in northern areas affected by heavy rain. Ministry executives have closely monitored the situation and prioritize maximum safety. The investigation into this incident is underway by authorized agencies, including the Department of Rail Transport and related bodies, which are collecting facts and preparing a report expected within 15 days.
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