Phetchaburi's lost tastes: nam phrik lam paen, phat ai khui and a dish to skip

Phetchaburi has long been known for its food, yet some of its dishes are now barely known even to younger locals. In fiscal year 2024, Thailand’s Department of Cultural Promotion, under the Ministry of Culture, ran a project called “Lost Taste” to record regional dishes at risk of disappearing. Phetchaburi’s three are nam phrik lam paen (น้ำพริกลำแพน), phat ai khui (ผัดไอ้ขุย) and khao niao khai mang da (ข้าวเหนียวไข่แมงดา, sticky rice with horseshoe crab eggs). This article covers what each one is, why it faded, and why the third is a story to know rather than a dish to hunt down.

What the Lost Taste project is

The project documents regional dishes from across Thailand, with a focus on cultural value, preparation and history. It is not a ranking of the tastiest food, and it is not a statement that every ingredient is safe.

UNESCO named Phetchaburi a Creative City of Gastronomy in 2021, the fifth Thai city after Phuket, Chiang Mai, Sukhothai and Bangkok. Locals call it the city of three flavours: sweet from palm sugar, salty from sea salt and sour from lime, all produced within the province.

All three dishes here come from the coast and the mangroves, especially Bang Tabun subdistrict in Ban Laem district, where a large mangrove forest sits at the river mouth and most people make a living from fishing and blood cockle farming.

Nam phrik lam paen: sourness from the mangroves

Lam paen is a mangrove tree, Sonneratia ovata. The PROSEA plant-use database describes its fruit as a flattened globe 3-5 cm across and 2-3 cm thick, dark green when young and yellowish-green when ripe. It is edible but very sour, sometimes used in place of vinegar.

Why use it at all? Because lime and tamarind are scarce in the mangroves, so people there used ripe lam paen instead. It is pounded into a shrimp-paste chili dip (nam phrik kapi), which gives a sourness and aroma unlike the usual lime version. It is eaten with blanched cha khram (a salty mangrove green) and grilled mullet, so the whole meal comes from the same shoreline.

The fruit appears only from January to May. Out of season the dish cannot be made, which is one reason it never travelled. PROSEA also notes that the tree is rather rare overall, growing as single trees among other mangroves rather than in stands.

Phat ai khui: a forgotten beef stir-fry

Phat ai khui is beef stir-fried with curry paste, several spices and Thai herbs. It is very hot and strongly aromatic. Its recorded home is the Ban Don Kai Tia community in Mueang Phetchaburi district.

This dish did not fade for lack of an ingredient, as lam paen did; it faded because fewer people cook it. Phetchaburi Rajabhat University has been presenting it to the public to revive it. The sources we read give no recipe or paste ratios, so we will not guess one. If you come across it at a cultural fair or a university event, ask the cook which spices go in.

Sticky rice with horseshoe crab eggs: know it, skip it

The third dish is sticky rice with sweetened horseshoe crab eggs. The recipe came down from a grandfather (“kong”) in Bang Tabun and dates to the late reign of King Rama V, when horseshoe crabs were plentiful and households there ate them routinely. The eggs are available only from January to April. Later, shredded coconut was added to stretch it for a whole family, and it became a sweet. The source article says the dish shows local knowledge of preparing the eggs safely.

We will be direct here: we do not recommend eating horseshoe crab eggs. Two horseshoe crab species live in the Gulf of Thailand, and the round-tailed one (Carcinoscorpius rotundicauda, called mang da thuai in Thai) has eggs that carry tetrodotoxin, the same toxin found in pufferfish.

A 2008 case series from Chon Buri Hospital lists four inaccurate beliefs: that toxic and safe crabs can be told apart, that a crab once safe is always safe, that heat destroys the toxin, and that safe eggs burst when heated.

Symptoms and what to do are covered in horseshoe crab egg poisoning. If anyone has a numb mouth or tongue after eating them, call 1669 (Thailand’s emergency medical number) straight away.

Worked example: egg season against case season

Put the numbers from the two sources side by side, step by step.

1. The eggs used for this dish are available January to April: 4 months.
2. The Chon Buri Hospital series covered 1994 to 2006 (13 years) and 280 patients, with cases peaking from December to March.
3. The two windows overlap for 3 months: January, February and March. The months when eggs are easiest to find are the months with the most patients.
4. Of the 245 patients with full records, 239 (97.5%) recovered completely, 5 died and 1 suffered brain damage from lack of oxygen.
5. That is roughly 280 ÷ 13 ≈ 21 patients a year, at one hospital.

Those numbers are why we tell this dish as history, not as a recommendation.

The three dishes compared

Dish	Main ingredients	Season	Why it faded	What to do
Nam phrik lam paen	Ripe lam paen, shrimp paste	Jan-May	Seasonal fruit, rather rare tree	Try it if you find it locally
Phat ai khui	Beef, curry paste, spices	All year	Fewer cooks	Try it; ask about the heat first
Sticky rice with horseshoe crab eggs	Horseshoe crab eggs, sticky rice, coconut	Jan-Apr	Fewer horseshoe crabs	Know it; do not eat it

Common mistakes

• Reading “lost” as “gone”. The project records dishes at risk. Some people still make them, especially for cultural events and community activities.
• Using lime and calling it nam phrik lam paen. You get an ordinary shrimp-paste dip. The point of the dish is the mangrove fruit.
• Believing long cooking makes horseshoe crab eggs safe. The research says the opposite: heat does not destroy the toxin.
• Treating a heritage record as a recommendation. Documenting cultural value and certifying food safety are different things.

Summary

Phetchaburi’s three Lost Taste dishes tell the story of mangrove communities. Nam phrik lam paen swaps lime for a sour mangrove fruit. Phat ai khui is a hot, fragrant beef stir-fry now being revived. Sticky rice with horseshoe crab eggs is heritage to know but not to try, because some horseshoe crab eggs carry a toxin that heat does not destroy. For the bigger picture of the province, read Phetchaburi, UNESCO City of Gastronomy, and for the regions overall, Thai food by region.

Sources

• Three traditional Phetchaburi dishes at risk of disappearing — The Nation Thailand
• Tetrodotoxin poisoning following ingestion of the toxic eggs of the horseshoe crab Carcinoscorpius rotundicauda, 1994-2006 — Southeast Asian J Trop Med Public Health (Mahidol)
• Sonneratia ovata (PROSEA) — Pl@ntUse
• Bang Tabun — Wikipedia