The Andaman Sea sits between Thailand's western coastline and the Andaman and Nicobar Islands of India, a deep, warm body of water fed by the Indian Ocean and shaped by two opposing monsoons that define the entire rhythm of fishing here. For visiting anglers, it represents Thailand's most prestigious offshore environment — a place where sailfish come in close enough to reach on a half-day charter, giant trevally patrol reef edges within sight of the islands, and liveaboard anglers can access open-water seamounts that few recreational boats have ever anchored over.
Understanding the Andaman means understanding its duality. The same weather system that shuts the fishery down from May through October — the southwest monsoon — is also what keeps the water clean and the nutrients cycling. When the northeast monsoon settles in around November, the sea flattens, the visibility goes blue, and the fishing opens with it.
What and Where
The Andaman fishing grounds are anchored at their northern end by Khao Lak and the Similans, and at their southern end by the Koh Rok and Koh Lanta area, with Phuket sitting roughly in the middle as the main logistics hub. Krabi serves as an eastern gateway for the southern reefs. Between these points, there are hundreds of kilometres of coastline, offshore banks, submerged pinnacles, and island chains, most of it underexplored by any standard.
The marinas at Chalong Bay in southern Phuket and the deep-water pier at Ao Po in the north are where the majority of day-charter and liveaboard vessels stage from. Tap Lamu pier, just south of Khao Lak, is the dedicated liveaboard gateway for Similan and Surin Islands trips, both national marine parks. For anglers targeting the southern grounds — Koh Rok, Hin Daeng, and beyond — Phuket charters are the most common departure point, though Krabi-based operators exist.
Geography note
The Andaman is deeper and more open-ocean in character than the Gulf of Thailand. Deepwater drop-offs start closer to shore, and the prevailing conditions — when they're good — are better suited to offshore pelagic fishing.
The Species Mix
The Andaman's signature catch is the Indo-Pacific sailfish (Istiophorus platypterus). These are not the Atlantic sailfish of the Caribbean — they run larger on average, with adults commonly in the 40–60 kg range and exceptional fish exceeding 80 kg. They're found throughout the Andaman but concentrate in the Koh Rok and Phi Phi corridor between January and March, drawn by bait concentrations that push up against the current lines.
Giant trevally (Caranx ignobilis) are the other headline species, particularly for anglers targeting reef structure and pinnacles. GTs in the 20–40 kg class are realistic targets around the Similan Islands and along the deeper reef drop-offs of the Racha Islands. Surface popping is the primary method, and the Andaman's clear water makes it genuinely sight-fishable in the right conditions.
Deeper in the water column, dogtooth tuna (Gymnosarda unicolor) are one of the most prized jigging targets on the Andaman. These are ambush predators built like barrels, capable of destroying medium-weight jigging tackle on the first run. They tend to associate with the same pinnacles and steep drop-offs that hold GTs, but deeper — typically 60–120 metres.
Blue marlin and black marlin are present, with blue marlin caught more consistently on the deeper offshore banks. They're not a primary target for most operators given the effort required and the rarity of encounters, but serious billfishers do run multi-day trips in search of them, particularly in the northern Andaman.
Reef species rounding out the card include coral grouper (Plectropomus leopardus), yellowfin grouper, bluefin trevally, Spanish mackerel (Scomberomorus commerson), barracuda, and yellow snapper. The reef system here is intact enough — particularly around national park areas — that the diversity is genuinely impressive compared to many Southeast Asian fisheries.
Season and Conditions
The Andaman fishes from November through April, with December through February being the sweet spot for most pelagic species. March is the prime sailfish month at Koh Rok, and April remains fishable but sees increasing southwesterly swell as the monsoon builds.
The southwest monsoon arrives in May and typically holds through October. During this period, conditions are frequently rough enough to make offshore fishing unpleasant at best and dangerous at worst. Most liveaboard operators suspend operations entirely from June through September, and many day-charter boats follow suit. October can see some weather windows, and experienced captains will fish them, but it's not a season to plan a trip around.
Sea surface temperatures range from around 27°C in January to 30°C+ by April, broadly within the comfort zone for billfish and tuna. Water clarity is generally excellent during the dry season, with 20+ metre visibility at many reef sites.
The northeast monsoon doesn't just bring good weather — it concentrates baitfish and creates the current lines that sailfish follow inshore.
Day Trip vs Liveaboard
The choice between a day charter and a liveaboard depends entirely on what you want to catch and how far you're willing to go.
Day trips from Chalong Bay can reach the Racha Islands in about an hour, making them genuinely practical for reef fishing, mid-range GT work, and trolling passes for Spanish mackerel and sailfish. A day trip won't get you to the Similans in any practical sense — it's too far. For anglers with limited time or those who want the comfort of a hotel at night, day trips are absolutely worth it, especially targeting the southern grounds.
Liveaboards unlock the whole fishery. A four- to five-day trip from Tap Lamu will give you multiple days around the Similan Islands group, the option to push to the Surin Islands further north, and nights anchored in calm bays with fishing from dawn to last light. Costs vary significantly by vessel standard, but a typical liveaboard runs around 1,200–2,500 USD per person for a four-day trip, with tackle and some meals included. The range reflects a wide spread between budget dive-converted boats taking on fishing passengers and purpose-built sportfishers with outriggers, fighting chairs, and proper tackle storage.
Techniques
Trolling is the backbone of most day charters and accounts for the majority of sailfish, mackerel, and barracuda catches. Standard high-speed trolling with lures and rigged ballyhoo covers the most water and produces consistently. Slower trolling with live baits — particularly live scad — can be devastatingly effective for sailfish when the concentrations are located.
Surface popping around reef structure is the method of choice for GTs. The technique demands commitment — heavy casting into the wind, working large poppers and stickbaits across the face of pinnacles — but the visual aggression of GT strikes makes it addictive. Dawn and dusk pushes around the right structure produce the most action.
Jigging opens up dogtooth tuna, amberjack, and large grouper. Slow-pitch jigging has gained significant traction with Andaman operators over the last decade, and purpose-built slow-pitch setups are worth bringing or renting. High-speed vertical jigging also works, particularly on the deeper seamounts.
Bottom fishing with live or dead bait is less glamorous but produces consistent grouper and snapper, particularly for anglers on family-style charters who want action rather than hunting pelagics.
Tackle That Works
For sailfish trolling, stand-up outfits in the 20–30 lb class are appropriate, with lever-drag reels holding 400+ metres of 30 lb mono or equivalent braid. Most operators have gear available, though it's rarely the quality a serious angler would bring themselves.
For GT popping, the standard is a heavy spinning rod rated 60–100 lb, paired with a reel in the 14000–20000 class with a braid mainline in the 80–100 lb range. A 60–100 lb fluorocarbon leader of 1–2 metres is standard. Poppers and stickbaits in the 100–200 gram range are the working lures.
For jigging, a medium-heavy jigging rod rated to 300–400 gram jig weight is appropriate for the depths commonly fished. A high-capacity spinning reel or low-profile overhead paired with 50–65 lb braid handles the mechanical demands. Jig weights of 200–350 grams cover most scenarios, with the heavier end used on deeper banks in current.
The Operator Landscape
The quality gap between Andaman operators is significant. At the top end, you'll find specialist sportfishing charters with vessels designed or converted specifically for fishing — proper outriggers, fighting chairs, live bait wells, quality rod storage, and captains who know the grounds. These operators typically run fewer passengers, keep tackle in good condition, and understand technique-specific fishing rather than running the same trolling pattern regardless of conditions.
At the budget end, converted dive boats or general tour vessels occasionally offer fishing as an add-on. The fishing is often secondary, the tackle is old, and the captain may not have deep knowledge of GT or jigging grounds.
For liveaboards, look for vessels with a dedicated fishing focus — not fishing as an afterthought to dive itineraries. The best Andaman liveaboards carry multiple rod-and-reel setups per angler, have fish-finding electronics in working order, know the timing of tidal windows around specific pinnacles, and employ a deckhand or guide who can rig leaders and assist with technique.
Conservation and Ethics
The Andaman is a billfish catch-and-release fishery in spirit if not always in law. The overwhelming consensus among reputable operators, and among serious sport anglers who fish here, is that sailfish and marlin should be brought to the boat and released. Billfish in Thailand have no robust commercial fishery protection structure — it falls to the sportfishing community to maintain self-imposed standards. If you're booking a charter, confirm the operator's release policy before you go.
GTs and reef species are also worth handling thoughtfully. In many parts of Thailand, reef fish are freely retained for consumption, which is understandable in a subsistence context. But catch-and-release of larger GTs — particularly spawning-size fish — maintains the quality of the fishery for everyone. A quick fight, a hook removal at the surface, and a strong release is the standard any serious angler should hold to.
The Similan and Surin Islands are national marine parks. Fishing within park boundaries is restricted, and this is enforced with increasing seriousness. Know where the boundaries are, and ensure your liveaboard operator does too.
Where to Go Next
The Andaman is big, and this overview only touches the surface. Dive deeper into specific grounds with these guides:
- Similan Islands fishing — the liveaboard destination that defines Andaman sport fishing
- Racha Yai and Racha Noi — the day-trip reef fishery south of Phuket
- Koh Rok sailfish — where the billfish numbers stack up in January–March
- GT popping tackle guide — what you need in your hands when the GTs are on
- Best time to fish in Thailand — the full seasonal breakdown across both coasts
