What began as a traffic accident in Pattaya has rapidly escalated into a major criminal investigation after police uncovered illegal weapons and a large stockpile at a residence, along with possible links to cross-border scam networks.
The case centres on Sun Mingchen, a 31-year-old Chinese national whose overturned car in Chon Buri province led police to discover illegal firearms and triggered a widening probe into his activities, finances and associates.
The investigation began on the evening of May 8, when officers from Na Jomtien police station responded to reports of a sedan overturning in Chon Buri's Bang Lamung district. None of the occupants -- Mr Sun, who was driving, and a Taiwanese woman travelling with him -- were seriously injured.
However, officers became suspicious after discovering a handgun inside the vehicle. The find prompted police to detain Mr Sun and broaden the investigation.
A subsequent search of his residence in tambon Huai Yai uncovered what authorities described as a large weapons stockpile. The cache reportedly included military-style rifles such as M16s, C4 explosives, ammunition, body armour and explosive-related equipment.
Thai media reports said some of the devices appeared consistent with booby traps, while others resembled components of suicide vests.
The discovery immediately raised security concerns and prompted a wider multi-agency investigation.
Mr Sun's account -- and police doubts
During questioning, Mr Sun told investigators he was a firearms enthusiast who had purchased the weapons online as part of a personal collection.
He also claimed he suffered from depression and intended to use the weapons to take his own life.
Police said the explanation did not convince them.
Pol Lt Gen Trairong Piwpan, spokesperson for the Royal Thai Police, said investigators were continuing to examine the intended purpose of the weapons and whether they were linked to broader criminal activity.
The case drew further attention after unverified claims circulated online alleging Mr Sun had used ChatGPT to seek advice about sabotage. Authorities later clarified that investigators had found only general searches related to firearms and weapons.
Questions over identity and background
As the investigation expanded, authorities began scrutinising Mr Sun's background and travel history.
Police said he had travelled frequently and entered Thailand several times since 2020, most recently on Jan 27 using a re-entry visa. He was also found to hold a pink identification card issued to non-Thai nationals residing in Thailand.
Online speculation later suggested he may have used another identity to obtain Thai citizenship.
The Department of Provincial Administration rejected the claim, saying the Thai citizen identified online was a separate individual who had legally acquired Thai nationality years earlier.
Police also questioned Mr Sun's former Thai wife after tracing addresses linked to his registration documents.
Investigators said the couple married in 2021 before divorcing last year. His ex-wife reportedly told police that her name had been used in multiple legal and business registrations connected to Mr Sun's rental car operations and other ventures.
Links to Cambodian scam networks
Police say there is no evidence Mr Sun planned attacks inside Thailand. However, investigators believe the weapons may be connected to organised criminal activity across the border.
Cybercrime officers examining financial records reportedly found transactions worth tens of millions of baht linked to bank accounts and cryptocurrency wallets allegedly associated with scam networks operating in Cambodia.
Authorities also uncovered chat records, weapons-training images and other material suggesting Mr Sun had been accumulating weapons since late last year. Investigators believe the arsenal may have been intended for use in conflicts or protection among rival scam syndicates operating across the border.
Thai military affairs journalist Wassana Nanuam, citing unnamed security sources, claimed Mr Sun was a senior figure within such networks and had used Thailand as a safe base.
Responding to the claim, National Intelligence Agency chief Thanat Suwannanon said authorities had identified links between Mr Sun and scam operations but could not confirm whether he held a leadership role.
Focus on illegal firearms transfers
The investigation has also raised questions about how restricted firearms entered circulation.
Metropolitan Police Bureau chief Pol Lt Gen Sayam Boonsom said several handguns seized from Mr Sun were originally police welfare firearms issued to officers under special procurement schemes.
Under Thai regulations, such weapons are not permitted for general resale and may only be transferred to heirs.
Police believe some of the guns changed hands multiple times before reaching Mr Sun, with at least one transfer dating back to 2011.
The findings have triggered investigations into current and former officers suspected of involvement in illegal firearm transfers.
Detention and medical treatment
Following his arrest, Mr Sun was held at a police station in Pattaya, where authorities said he refused food for several days and appeared to be under severe stress. He was transferred to Pattaya Remand Prison on May 11 but was later taken to hospital after reportedly suffering seizures.
The Department of Corrections said medical staff found indications of an overdose involving personal medication. He was treated in intensive care before later stabilising.
Officials said he remains under close supervision to prevent further attempts to harm himself.
Expanding investigation
Police have charged at least five Thai suspects in connection with the weapons network. They include current and former military personnel, a shooting-range trainer and an individual accused of providing bank accounts used in arms transactions.
All have denied the allegations and were released pending further investigation.
Authorities said they are continuing to examine companies linked to Mr Sun, his financial activities, and possible connections to organised crime.
For now, police maintain the investigation points to organised crime rather than terrorism. But the discovery of explosives, military-style weapons and alleged scam network links has ensured the case remains under intense public scrutiny.
