Gulf of Thailand — December 2026 Fishing Report
December brings the Gulf of Thailand fishing to its annual maximum. The northeast monsoon is at full operational strength, the sea state across the central and southern Gulf is organised and manageable, and the offshore species that define the Gulf's international fishing reputation are present in their peak December numbers. At Chumphon, the sailfish season is at its density maximum — double-hookup days are achievable targets rather than exceptional events. At Koh Tao, the GT fishing on the island's rock structures is at its December best, with fish that have been feeding through the entire cool season now in prime physical condition. Spanish mackerel, wahoo, and yellowfin tuna complete a December offshore species list that makes the Gulf one of Southeast Asia's most productive cool-season fisheries.
Water and Weather
December sea conditions in the central Gulf are the result of the northeast monsoon's full establishment. Northeast wind at 10–20 knots is the consistent baseline, generating 1–2 metre northeast swell across the open Gulf. For most of the Gulf's major fishing departure ports — Chumphon, Pattaya, Hua Hin — this swell direction is relatively benign. The Chumphon offshore grounds are effectively sheltered from the northeast by the mass of mainland Thailand, meaning the Chumphon Bank regularly sees calmer conditions than might be expected from the wind forecast.
Sea surface temperatures in December are at the annual minimum for the Gulf — 26–27°C in the offshore zone. This temperature activates the sailfish and tuna feeding cycles that define the Gulf's December calendar. Water clarity on the offshore grounds is excellent: 15–20 metres at the Chumphon Bank, 20–25 metres around Koh Tao's outer reef structures.
The Koh Samui and Koh Phangan area of the upper southern Gulf faces northeast and receives the full strength of the December monsoon swell on its eastern beaches. Shore fishing and small-boat operations on Koh Samui's east coast are significantly affected by December's 2–3 metre northeast swell; however, the island's western coast and the waters south of Koh Tao are largely protected.
What's Biting Now
Sailfish — Chumphon Bank sailfish are at December's peak concentration. The baitfish aggregations on the Bank structure — driven by the northeast current's nutrient transport — attract sailfish in numbers that make consistent encounters achievable for capable charter boats with experienced crews. Circle-hook rigged live garfish under floating balloons remains the most effective and sporting technique. December's productive days see 5–10 sailfish encounters with 3–5 landed on a typical full-day program.
Giant trevally — Koh Tao's December GT fishing is at the cool season's finest. The fish are at peak physical condition after four months of productive feeding, and the December water clarity — the year's best — enables precise surface presentations to visible fish patrolling the rocky structures. Dawn and dusk sessions on PE6-8 gear with large poppers; fish averaging 10–25kg.
Wahoo — December wahoo are present throughout the Gulf's offshore zone in increasing numbers as the cool, clear water spreads from the southeast. High-speed trolling between pinnacle stops and along the offshore bank edges produces wahoo from 10–25kg. The species is increasingly accessible from Chumphon in December compared to October and November.
Yellowfin tuna — The Chumphon Bank continues to hold yellowfin through December. A full-day offshore charter at Chumphon in December can produce a mixed bag of sailfish, wahoo, and yellowfin tuna alongside the reef species encountered at the pinnacle stops.
Spanish mackerel — Available everywhere from Pattaya to the Malaysia border. The December run of narrow-barred mackerel through the offshore reef and current systems produces consistent catches for trolling and jigging anglers across all Gulf fishing ports. An underrated December target given the sailfish attention focused on Chumphon.
GT at Koh Samui offshore — While Koh Samui's east coast is rough in December, the fishing grounds to the south and west of the island — accessible from the island's western departure points — hold resident GT populations. Koh Mat Sum (Pig Island) and the offshore rocks southwest of Samui produce December GT fishing that is largely unknown to the general visiting public.
Reef snapper and grouper — December bottom fishing across the Gulf's offshore structures is exceptional. The clear, cool water brings reef fish onto the upper structure sections where fresh bait and large lure presentations produce consistent catches. Red snapper, mangrove jack, and coral grouper dominate the bottom fishing bags.
What to Target This Month
Top pick: Chumphon sailfish Christmas-week charter. The Gulf's premier December fishing experience. A 3-night Chumphon program over the Christmas week — arriving 23 December, fishing 24–26 December — delivers three full days on the Bank during the sailfish's peak December density. Watching a December Chumphon double-hookup from the stern — two sailfish tail-walking simultaneously in the clear Gulf water, 40 metres behind the boat — is a fishing experience that justifies the planning effort absolutely.
Second pick: Koh Tao GT and Chumphon sailfish combination. A 5-day itinerary that allocates 2 days to Koh Tao's GT rock sessions (dawn surface fishing) and 2 days to Chumphon sailfishing covers both the Gulf's December highlights efficiently. Travel between Koh Tao and Chumphon is by ferry (2 hours). This combination represents two of the Gulf's best species in their respective peak months within a single manageable trip from Bangkok.
Third pick: Pattaya offshore reef Christmas holiday session. The most Bangkok-accessible December option. A full-day Pattaya charter on any working day between 26 December and 2 January targets Spanish mackerel, barracuda, reef snapper, and trevally in excellent December conditions. The professional Pattaya charter fleet operates through the holiday period and the offshore conditions during this week are typically the December's best — calm, clear, and productive.
What to Avoid
Avoid Koh Samui's east coast for offshore fishing in December — the northeast monsoon swell on the east-facing beaches produces 2–3 metre conditions that make small-boat operations uncomfortable and unproductive. Avoid committing to multi-day Gulf coast accommodation bookings in the Christmas-New Year period without advance reservation — the Gulf islands and resorts fill to annual capacity in the final December week. Avoid last-minute December sailfish charter bookings at Chumphon without realistic expectations — the best boats and crews are fully committed weeks ahead, and walk-in charters during peak week may involve less experienced operators.
December Gulf Double-Hookup Protocol
Chumphon's December double-hookup situations require a practiced crew response to maximise success. The moment the first sailfish takes a live bait and the circle hook sets, the captain slows the boat while the second angler deploys their live garfish bait directly behind the vessel. The second fish — almost always visible following the first within 5–10 metres — typically takes within 30 seconds. Both fish then perform their aerial series simultaneously. An experienced Chumphon crew will have landed both fish within 15–20 minutes. Practicing the transition between the first hook-up call and the second bait deployment is the most important preparation a Chumphon visiting angler can do before departure.
Venue Spotlight
Chumphon Bank and Town (Chumphon Province) — December Chumphon is the Gulf's most concentrated fishing destination. The town's charter fleet operates from Tha Tapao Pier with multiple boats running full-day offshore programs to the Bank. The best December operators carry live-bait systems, are equipped for overnight accommodation on larger vessels, and have multi-year sailfish program experience. Chumphon town's restaurants and guesthouses are simple but comfortable, and the town itself has an authentic Thai provincial character that visiting international anglers often find more appealing than the overdeveloped beach resorts.
Koh Tao (Surat Thani Province) — December on Koh Tao offers the GT fishing season's finest conditions. The island's small-boat charter operators, primarily known for their dive tourism services, run dawn GT programs for fishing anglers who specifically request them. The island in December has excellent accommodation availability and prices are at transitional shoulder-season rates before the full New Year peak. The combination of the GT fishing at dawn, the world-class dive sites for afternoon, and the island's laid-back social scene makes a December Koh Tao fishing trip one of the Gulf's best holiday-season itineraries.
Pattaya Deep-Sea Fishing (Pattaya, Chonburi Province) — Pattaya's proximity to Bangkok (90 minutes), its professional charter fleet, and its comprehensive resort infrastructure make it the most logistically convenient December Gulf fishing option. The offshore reef and bank complex south of Pattaya produces Spanish mackerel, large barracuda, snapper, and trevally throughout December. The evening squid jigging from Pattaya pier is a social evening activity worth combining with an offshore day session.
Logistics in December
The Gulf's major December fishing destinations are all well-served by transport infrastructure. Chumphon: overnight train from Bangkok (8 hours) or direct van (6–7 hours). Koh Tao: ferry from Chumphon (2 hours), speedboat from Ko Samui or Ko Phangan, or direct from Don Sak Pier (Surat Thani). Pattaya: expressway from Bangkok (90 minutes). December accommodation across all destinations is at peak-season rates in the 20 December–5 January window — book early. Charter availability for prime December dates (24–31 December) should be confirmed by October at the latest for the best Chumphon sailfish operators.
Looking Ahead to January
January carries the Gulf's peak season forward into the New Year without any reduction in fishing quality. Sailfish remain concentrated at Chumphon through January. GT at Koh Tao are at their January best as the coolest water of the year arrives. The holiday crowds have departed, leaving the charter boats running their highest-quality programs for the serious anglers who plan their Gulf trips specifically around January's combination of outstanding fishing and post-holiday quiet.
