There is a fish lurking in Thailand's rivers that most Thai people have never seen alive. Pangasius sanitwongsei — called the Chao Phraya catfish in English, pla thepa (ปลาเทพา) in Thai, and sometimes the dog-eating catfish or Paroon shark in the international trade — is one of Southeast Asia's most imperilled freshwater predators. Historical accounts from the nineteenth and early twentieth centuries describe fish of extraordinary size: specimens several metres long hauled from the deep bends of the Chao Phraya, creatures capable of swallowing dogs that fell from the stilt-houses above. Today, catching one at all is a minor miracle. Catching one in the wild is something that almost nobody does anymore.
Identification and Biology
At a glance, the Chao Phraya catfish could be confused with its more famous cousin the Mekong giant catfish, but the two species lead entirely different lives. The Mekong giant catfish (Pangasianodon gigas) is a filter feeder, sieving algae and plankton from the water column through modified gill rakers, its mouth wide and toothless. The Chao Phraya catfish is a predator. Its mouth is narrower, more pointed, lined with fine recurved teeth, and backed by the muscular jaws of an animal designed to chase and grip. Look at the fins: the Chao Phraya catfish carries dramatically elongated pectoral fins that sweep back like scimitars, and an equally striking, sickle-shaped dorsal fin. These fins are not decorative; they make the fish conspicuous in the water and give it the alternative common name of Paroon shark, a reference to the silhouette it cuts when cruising close to the surface.
The body is torpedo-shaped and pale grey, lighter on the belly, with smooth scaleless skin that shimmers silver-blue in clear water. Juveniles carry faint lateral banding that fades as the fish matures. Adults grow to lengths exceeding two metres. Weights above one hundred kilograms, while exceptional in the modern era, are biologically plausible given the species' documented history — though any angler who lands a fish much above fifty kilograms today should consider themselves extraordinarily fortunate.
Pangasius sanitwongsei belongs to the family Pangasiidae, the shark catfishes of Southeast Asia, and its range historically spanned the Chao Phraya, Mae Klong, and Mekong river systems. It is a migratory fish that in its natural lifecycle would have moved upriver to spawn in seasonal floods, returning to deep holding pools in the dry season. Those natural migration routes have been fragmented by dams, weirs, and floodplain development across the region. The IUCN lists the species as Critically Endangered. Wild populations are considered severely reduced, and the fish is rarely caught commercially.
Where to Catch It in Thailand
For the practical angler, the Chao Phraya catfish now exists primarily within managed fisheries. Bungsamran Lake in Bangkok is the most famous venue associated with this species, and rightly so — the lake's long history and its deliberately diverse stocking programme mean it holds some of the largest predatory catfish accessible to visiting anglers anywhere in the world. Bungsamran's population includes fish that have been growing in the lake for many years, and specimens in the thirty-to-eighty-kilogram range are a genuine possibility on any given session.
Other managed venues in Bangkok and the surrounding provinces have also stocked the species, though availability varies. Before booking a session anywhere specifically targeting pla thepa, confirm with the venue directly that the fish are present and active — stocking levels fluctuate and honest venue managers will tell you what is running.
Wild fish in the lower Chao Phraya river, between Bangkok and the Gulf of Thailand, are occasionally reported as bycatch by local commercial fishermen, but these encounters are rare and often involve smaller, younger fish rather than the mature giants of legend. Targeting the species deliberately in the wild is both legally complex — possession and trade of the fish are restricted — and practically very difficult. The managed lake circuit is the realistic option for almost every angler.
Not the same as the Mekong Giant
The Chao Phraya catfish is frequently confused with the Mekong giant catfish at fishing venues. Key distinctions: the Chao Phraya catfish has a narrower, more pointed snout, visible teeth, dramatically elongated pectoral and dorsal fins, and a predatory diet. It is a different species with a different personality on the line.
Best Season and Conditions
Cool-season fishing — November through February — offers the best consistent results at managed venues. Water temperatures drop from the stifling highs of the wet season into the mid-twenties Celsius, and fish that have been lethargic through the hottest months become noticeably more active and aggressive on the feed. Feeding windows tend to concentrate around dawn and dusk during the cool season, though Bungsamran fishes around the clock and takes from large catfish can come at any hour.
The transition months — October as the rains ease, and March as temperatures begin climbing — also fish well. Full summer, from April into September, is harder work. The fish remain catchable but feeding is less predictable, and the heat makes long sessions genuinely uncomfortable. Bring shade, bring water, and lower your expectations slightly in peak summer.
Techniques and Tactics
The Chao Phraya catfish is a bait angler's fish, full stop. Lures and flies are not meaningful options for a species that hunts by scent and ambush in murky river water. This is rod-and-reel fishing of the most elemental kind: a big bait presented on the bottom, a heavy rod in a rest, and patience.
At Bungsamran and similar venues, the standard approach involves a large dead or live fish bait — typically sections of mackerel, whole small tilapia or feeder fish, or chunks of fresh squid. Bait presentation is straightforward: the bait is hair-rigged or side-hooked on a large, strong single hook, with a heavy inline or running lead that pins it firmly to the lakebed. Chao Phraya catfish are primarily bottom feeders in their adult stage, and a bait drifting off the bottom will be ignored.
Running rigs are preferred over fixed leads so that a taking fish can move with the bait for a moment before hitting resistance. The take itself is usually unmistakable — a slow, powerful pull rather than a sharp smash, the rod bending in a deep arc as the fish turns away with the bait. Resist the urge to strike immediately; give the fish a second or two to turn the bait in its mouth before engaging the reel and setting the hook firmly.
Bait size matters. The Chao Phraya catfish is a large predator and responds better to substantial offerings — half a small mackerel or a whole tilapia of three hundred grams is not excessive. Small baits often produce small fish, or no fish at all. Scent is important: fresh bait out-fishes frozen bait, and at venues where multiple anglers are fishing, keeping bait rotation quick helps maintain attractiveness.
Tackle Setup
This is not a species that forgives undergunned tackle. Even a modest specimen of thirty kilograms in an enclosed lake will use its size and those extraordinary pectoral fins to cover ground aggressively, and a fish over fifty kilograms is a genuine physical challenge.
Heavy carp and catfish rods in the three-to-five-pound test-curve range are appropriate — long enough to cast a heavy lead with confidence, stiff enough in the butt to lever the fish's head during the fight. Match these with a robust large-arbour fixed-spool or a heavy baitrunner reel loaded with braid of at least eighty-pound breaking strain. Monofilament mainlines have their advocates at some venues, and the stretch can be forgiving on initial runs, but braided lines dominate at the serious big-fish venues because they allow better sensitivity and no-compromise hook sets.
Leaders should be heavy monofilament or fluorocarbon — at least one hundred pounds — long enough to withstand the abrasion of the fish rolling against the line near the rod tip. Hooks should be strong single patterns in the 6/0-to-10/0 range: circle hooks or wide-gap patterns suit this style of fishing well. Check hooks for sharpness before every bait, and check the leader for nicks after every run, whether you land the fish or not.
Rod rests, bite alarms, and a comfortable unhooking mat are standard kit. You may be waiting hours between takes, and when a take comes, having everything arranged so that you can respond efficiently and handle the fish safely matters.
Records and Notable Catches
Formal IGFA record recognition for Pangasius sanitwongsei is complicated by the species' status and historical catch documentation. Verified catches above one hundred kilograms have been reported from managed venues over the years, and several claimed catches from the Chao Phraya river system before the species' population declined suggest fish of truly exceptional size. Without corroborated weights and measurements, specific figures from historical accounts should be treated cautiously. The largest fish caught in managed Thai venues in recent memory have reportedly ranged from around eighty to over one hundred kilograms, though venues rarely publicise exact figures.
What is not in doubt is that this fish holds the potential to grow to a size that humbles most freshwater anglers. Even a fifty-kilogram specimen, modest by historical standards, is a fish that will test both angler and equipment thoroughly.
Conservation and Ethics
The Chao Phraya catfish is Critically Endangered in the wild. That designation is not bureaucratic caution — it reflects a genuine collapse of wild populations over the past century driven by overfishing, habitat loss, dam construction, and pollution of the river systems on which the species depends. The fish still exists in part because of managed fishery stocking, a biological irony that has kept the species visible to anglers even as its wild counterpart has all but disappeared.
To hold a Chao Phraya catfish is to hold a creature that has almost vanished from the earth. Handle it accordingly.
Catch-and-release is not merely etiquette at venues that hold this species — it is the correct response to the situation. Handle fish minimally, keep them in the water as much as possible during photography, and return them promptly. Never purchase or consume Chao Phraya catfish: the trade in wild-caught specimens, even where it occurs informally, directly threatens the species' survival. Managed venues that stock the fish should be asked what steps they take to breed and replenish their populations — responsible venues can give meaningful answers.
If you observe what appears to be a pla thepa in the wild during a river session targeting other species, photograph and document it if you can, and report it to the local fisheries department. Wild sightings are scientifically valuable.
What It's Like to Hook One
The take arrives quietly, at least at first. The rod tip loads slowly, not with the sudden violence of a predatory snakehead strike or the electric jolt of a big barramundi. The baitrunner yields line, and then the rod doubles over as something very large moves away with a sense of absolute purpose.
Chao Phraya catfish do not jump. They do not greyhound across the surface or peel off searing runs into open water in the fashion of a saltwater species. What they do is use their body — all of it — and those enormous fins, setting their pectorals against the water like sea anchors and pulling in directions that feel impossibly powerful given the speed involved. Gaining line on a large fish is a process of patience and persistence, applying pressure at angles to turn the head, recovering a metre at a time, being ready to give back what was just taken when the fish decides to run again.
Proximity to the bank or landing zone does not mean the fight is over. Fish that are almost beaten will find reserve energy when they see the net or feel shallow water, running again with surprising power. The final minutes of a big-fish fight are where tackle fails and hearts are lost — stay focused, keep the line clear, and trust the gear.
When it finally rolls into the net, the Chao Phraya catfish is arresting up close. The smooth, pale skin, the extraordinary fin length, the intelligent curve of the jaw — this is a creature of real antiquity, a species that was swimming these rivers when the city above it barely existed. Hold it carefully, low over the water, long enough for a photograph if conditions allow, and then watch it kick back into the dark.
Plan Your Session
Targeting the Chao Phraya catfish pairs naturally with time at Bungsamran Lake, the most storied big-catfish venue in Southeast Asia. For comparison, giant Mekong catfish share similar water at several venues and make an instructive contrast. Anglers interested in other large predatory catfish should also consider the Amazon redtail catfish, an introduced species with a very different personality on the rod.
Practical planning is helped by our Bangkok fishing location guide, and before any session in Thailand, check the fishing licence guide for tourists and our catch-and-release best practice notes.
