Gulf of Thailand spearfishing: Chumphon, Koh Tao, and the mainland coast

The Gulf of Thailand is the quieter spearo option. Lower visibility than the Andaman, fewer pelagics, but also fewer tourists, softer currents, and far more legal coastline per square kilometre. I have spent years hunting these waters as the official Rob Allen distributor in Thailand. This is the practical guide — where you can legally hunt, what you will see, and when to plan your trips.

For the broader legal framework, start with our legality and marine parks guide. This post assumes you already know the core rule: spearfishing is legal in Thailand outside national marine parks.

The short version

• Hunt the mainland coast from Chumphon south to Koh Samui. Not the islands inside Mu Ko Chumphon or Ang Thong parks.
• Koh Tao itself is legal outside the Shark Island and pinnacle formations, but check with a local before every trip — boundaries shift.
• Best season: November to April. Visibility 8-15 m, seas calmest. Monsoon runs May to October.
• Target fish: grouper, snapper, trevally, cobia, queenfish. Occasional mid-range dogtooth on the deeper edges.
• Typical kit: 75-90 cm Snapper railgun, 14 mm rubber, 7 mm shaft. No need for a bluewater setup unless you are heading offshore.

Legal coastline, in detail

The Gulf’s biggest advantage over the Andaman is how much coastline sits outside park boundaries. You do not need a boat to hunt — shore dives from the right beach produce results.

Chumphon mainland

The stretch from Hua Hin south through Chumphon town is almost entirely legal for spearfishing. Rocky headlands between beaches hold grouper and snapper. The water is often murky close to shore, but a short swim out past the sand zone usually clears to 5-8 m visibility. Avoid Mu Ko Chumphon National Marine Park (offshore islands including Koh Ngam Yai, Koh Ngam Noi, Koh Rang Kajiu, Koh Mattra). These are popular scuba sites precisely because fishing is banned there — the same reason you cannot spear them.

Koh Samui (non-park zones)

The northern and western coasts of Koh Samui fall outside Ang Thong National Marine Park. Legal hunting grounds include the reefs off Choeng Mon, Big Buddha, Bophut, and the west coast down to Lipa Noi. The southern reefs around Hua Thanon and Lamai are also legal and productive — this is where I base myself and run trips from.

Do not hunt Ang Thong Marine Park. The dramatic cliff islands north-west of Samui are all protected. Fines are serious and the rangers patrol during high season.

Koh Tao

Koh Tao is a grey zone. The island itself is not inside a declared marine park, but specific dive sites like Sail Rock, Chumphon Pinnacle, Shark Island, and Southwest Pinnacle are off-limits because they are commercial scuba sites protected by local agreements. You can hunt the less-visited western and southern shores legally, but always ask a local on arrival. Rules shift.

Prachuap Khiri Khan and Hua Hin

The whole coast from Cha-Am to Khao Tao is legal with a few small exceptions around wildlife refuges. Water is typically 3-6 m visibility. Good for reef fish training dives. Not a destination coast — but useful if you live in Bangkok and want a same-day drive.

Fish you will actually see

Let us be honest about the Gulf: it is not the Andaman. Bluewater pelagics are rare inshore. But the reef species list is strong if you know what to look for.

• Mangrove snapper (กะพงแดง) — the staple. Holds in holes and overhangs from 3-12 m. Moves fast. Take with a short shot, 75 cm gun is fine.
• Orange-spotted grouper (ปลาเก๋า) — holds deep in rock piles. Patient hunting. Do not overshoot — a 90 cm railgun through a 3 kg fish will wreck the shaft if it hits coral behind. Aim precisely.
• Giant trevally (GT) — smaller inshore class, 3-8 kg typically. Opportunistic. Happens more often on outer reefs past 10 m depth.
• Queenfish — mid-water roamers. Flash-hunt with a plug fish if you spot one from above.
• Emperor fish — big-lip species that cruise the reef edge. Underrated eating. Common in Chumphon.
• Cobia — surprise guests at mooring buoys and FAD structures. If you see one, shoot. They do not wait.
• Dogtooth tuna (small class) — 5-10 kg class shows up on the deeper offshore pinnacles, especially around Koh Tao. Rare but real.

Season — the honest calendar

Month	Visibility	Wind / sea	Spearfishing rating
November	5-8 m	Calm	★★★★ (start of prime)
December	8-12 m	Calm	★★★★★
January	10-15 m	Very calm	★★★★★
February	10-15 m	Calm	★★★★★
March	8-12 m	Calm	★★★★
April	5-8 m	Warmer, calm	★★★
May	3-6 m	Rainy, choppier	★★
June-Sep	2-5 m	Monsoon, squalls	★ (skip)
October	3-6 m	Transition, unpredictable	★★

The monsoon months (May through October) are a write-off for Gulf spearfishing. Too much stirred silt, too many afternoon squalls. Use that time for dry training — our breath-hold trainer runs CO2 and O2 tables from your static max.

Kit for the Gulf

You do not need bluewater gear for Gulf spearfishing. Overkit is tiring and catches on the reef.

• Speargun: 75 or 90 cm Snapper railgun, single or double 14 mm. A 90 cm handles everything from hole-snaps to mid-range trevally.
• Wetsuit: 1.5 mm open-cell with hood. Tropical-weight. Anything thicker is overkill and uncomfortable at 28 °C surface temperatures.
• Fins: plastic or glass-fibre blades are fine. Carbon is fragile on Gulf reefs — too many rock contacts in low visibility.
• Float + line: 7-12 L float with 15-20 m line. Flag non-negotiable.
• Mask: low-volume clear-skirt. Amber lens helps in low-viz water.

If you want a curated full kit in one order, the Reef Starter Kit bundles all of the above at 12% off.

Training path

Gulf spearfishing forgives poor technique more than the Andaman does — shorter shots, less current, more hole-holding — but the safety stakes are identical. Blackouts happen at 6 m just as easily as at 20 m. Before your first season, get properly certified. Freediving Koh Samui runs Apnea Total Level 1 from Lamai in 3 days for 9,500 THB.

One honest warning

Visibility in the Gulf is often bad. If you show up expecting Similans-clear water, you will be disappointed. Come with a mindset of hole-hunting and slow stalking, not open-water ambush. The fish are there. They are just harder to see, and that is what makes Gulf hunting a skill game more than a gear game.

Got a specific coast or island you want advice on? Message me on WhatsApp with your dates — I’ll tell you straight if it is worth the trip.