Giant trevally are not a year-round proposition on Thailand's Andaman coast. The southwest monsoon that batters the western seaboard from May to October makes offshore fishing impractical and sometimes dangerous. What Thailand offers is a defined, high-quality season — November through April — that aligns with the northeast monsoon's calming influence on Andaman conditions and produces some of Southeast Asia's most compelling GT popping fishing.
If you are planning a dedicated GT trip, the calendar answer is straightforward. The how-to-choose-within-that-window is more interesting.
Understanding the Andaman Season
Thailand's Andaman Sea is governed by two monsoons. The southwest monsoon (May to October) pushes large swells against the west-facing coast, making offshore navigation difficult and reducing water clarity as wave action disturbs coastal sediments. The northeast monsoon (November to April) reverses the pattern — prevailing winds arrive from the east, sheltering the Andaman coast and delivering the settled conditions that make offshore and island fishing possible.
For GT popping specifically, clear water is important. Giant trevally use vision to target and intercept fast-moving surface lures, and the visibility advantage of the dry-season Andaman — where water around the Similan and Surin island groups can be exceptional — makes a measurable difference to fishing quality compared to the murky conditions of a post-monsoon coastal zone.
The November to April season is shared across all offshore fishing on Thailand's Andaman coast — from reef fishing to sailfish and GT popping. Charter availability, boat traffic, and accommodation at departure points like Khao Lak all peak during this window. Book well ahead for December, January, and any period around the full or new moon.
The Lunar Advantage: Timing Within the Season
Within the November-to-April window, not all weeks are equal. GT fishing — particularly popping for large fish — is significantly influenced by tidal phase, and tidal strength in the Andaman is tied to lunar cycles.
The days around the full moon and new moon produce the strongest tidal movements. Strong tidal pushes concentrate baitfish around headlands, channel edges, and the vertical walls of island limestone formations — exactly the environments that GT use for ambushing prey. When bait is pushed and concentrating, trevally activity spikes.
Experienced GT guides in Thailand build their trip calendars around these lunar windows, scheduling multi-day expeditions to place the maximum fishing time around the two or three days either side of each new and full moon. The difference between a high-lunar-activity trip and a weak mid-cycle trip can be significant in terms of the number of quality strikes and the size of fish encountered.
Experienced captains can look at a lunar calendar and a weather forecast and tell you, within a day or two, exactly when the Andaman GT window will be at its sharpest for any given month.
Month by Month: The Andaman GT Calendar
November: Season opens but conditions can be variable. Early northeast monsoon swells linger and water clarity builds through the month. Fishing is available but represents a step down in reliability from peak months.
December: Conditions typically settle and GT activity picks up strongly. December is a popular month for visiting anglers, combining good fishing with the appeal of being in Thailand over the festive period. Book early — boats fill fast.
January: Often cited alongside February as the most reliable month of the season. Conditions are settled, water is clear, and GT are active around the island structures that make Andaman popping distinctive. Lunar windows in January can produce exceptional sessions.
February and March: Peak months for many experienced GT anglers. Wind is typically lightest, seas most settled, and visibility at its best. March brings slightly warming water as the season approaches its end, which can trigger particularly aggressive GT feeding behaviour.
April: The season's last reliable month. Conditions begin to deteriorate toward the end of April as the southwest monsoon builds, and departure times become less predictable. Early April in a stable year can still be excellent, but booking flexibility is advisable.
If you can only choose one month for a Andaman GT trip, February offers the best combination of settled conditions, strong lunar windows, and pre-season availability before March becomes the busiest month for visiting sport anglers.
Sea Conditions and What to Look For
Perfect popping conditions for GT involve a light breeze creating gentle surface texture — enough to break up the silhouette of the angler on the deck but not enough to make long casts difficult. Flat calm can produce excellent early-morning topwater sessions but reduces the ability to work large poppers effectively through the retrieve.
A light current running around headlands and island points is ideal. This is where bait congregates and where GT position themselves. The tidal push associated with full and new moon phases creates exactly this kind of current movement at productive locations.
Heavy swells reduce practical fishing time and make accurate popper presentation difficult. Post-storm periods with residual swell but clearing skies are worth fishing as GT feeding activity often spikes when settled conditions return.
Gear and Charter Considerations
GT popping on the Andaman demands serious tackle. This is not a fishery where lighter gear is a creative choice — it is a choice that results in lost fish and broken tackle. For equipment specifics, the GT popping tackle guide covers rods, reels, line, and leader in detail.
For booking a popping charter or liveaboard that accesses the prime GT grounds, see liveaboard fishing Thailand and popping charter Thailand.
For the full GT species profile — biology, behaviour, size records, and why this fish has become a global benchmark for inshore saltwater sport fishing — visit the giant trevally species page.
