Arapaima — the prehistoric giant of Amazonian rivers — has found a second home in Thailand's specialist fishing lakes. Stocked at a handful of carefully managed venues, they are now among the most sought-after species on the Thai exotic fishing circuit. Reaching well over 100 kg in some cases, a landed arapaima is a genuinely life-list fish for most visiting anglers.
The good news for planning purposes: arapaima are available to catch every month of the year at the venues that hold them. The slightly more nuanced truth is that certain conditions make for dramatically better sessions.
The Short Answer
Year-round fishing is possible, but November through April offers the most productive conditions. Within this window, the cool-season months (November–February) deliver the most consistent surface activity, while March and April can produce explosive feeding as water temperatures begin to rise. Dawn sessions outperform any other time of day regardless of season.
Understanding Arapaima Behaviour in Thailand
Arapaima are obligate air breathers — they must surface periodically to gulp air or they drown. This biological necessity means they are more visible than almost any other freshwater fish, and it creates an unusual dynamic for anglers: you can see your quarry, often at close range, before you cast.
This surface-breathing habit is most pronounced and predictable in cooler conditions. When water temperatures are lower, arapaima appear to surface more frequently and spend more time in the upper water column. In the heat of the Thai summer — particularly from May through September — fish tend to hold deeper and surface less visibly, which makes locating and targeting them harder work.
If you can see arapaima rolling and surfacing regularly when you arrive at the lake, you are in the right session. Frequent surfacing indicates active, feedable fish. Rare or absent surfacing often means fish have dropped deep and will require more patience.
Cool Season (November–February): The Prime Window
November through February represents the best all-round arapaima fishing in Thailand. Cooler air and water temperatures encourage surface activity, fish seem to feed with more confidence, and the sessions themselves are comfortable to fish — a relevant consideration when you may be on the bank for eight or more hours.
Gillham's Fishing Resort in Krabi, the most famous arapaima venue in the country, sees its highest demand during these months from visiting European and American anglers. Booking well in advance is essential if you are targeting this window.
Early Warm Season (March–April): High Activity
As Thailand transitions from cool to hot, water temperatures rise quickly. For arapaima, this warming appears to trigger increased feeding activity — possibly related to spawning behaviour or metabolic acceleration as fish prepare for the hottest months. March in particular can produce some of the most active and aggressive arapaima fishing of the year.
"Early March sessions at Gillham's can be electric — fish rolling constantly, feeding on surface offerings, and fighting with maximum aggression. Some guides rate it as the single best arapaima month."
Hot and Wet Seasons (May–October): Still Fishable
Arapaima do not disappear during the hot and rainy months. Stocked venues maintain their fish populations regardless of season, and catches continue. The practical challenges are the heat (particularly from May to August), slightly less predictable surface behaviour, and the logistics of fishing through heavy rain in the wet season.
Overcast, rain-cooled days during the wet season can trigger surprisingly active feeding spells. Anglers who are flexible with timing — waiting for a break in the weather before heading to the lake — can find excellent conditions in what looks like an unpromising forecast.
Within the Day: When to Be on the Bank
- Pre-dawn to mid-morning: The most important window. Arapaima surface frequently at dawn, are visible and targetable, and seem to feed most aggressively in the first two to three hours of daylight.
- Late morning to early afternoon: Activity decreases. Fish may still be caught, but the pace drops noticeably.
- Late afternoon: A modest secondary window, particularly in the cool season.
Practical Takeaways
- November through February: Most comfortable and most consistent for surface activity.
- March–April: High potential for aggressive feeding, particularly at dawn.
- Arrive before sunrise and be baited up and ready at first light.
- Book Gillham's well in advance for cool-season dates — demand is high and swims are limited.
- Rain is not necessarily bad news — overcast conditions often improve arapaima feeding behaviour.
For full species details, tackle selection, and venue comparisons, see the complete Arapaima species guide.
