The hook
One of the oldest cities in Thailand, holding a temple many Thais consider the most revered in the south — in a province with jungle, mountains and beaches that international visitors pass straight through on the way to the islands.
01Why it's worth it
Wat Phra Mahathat Woramahawihan is the reason the city exists in its present form. Its enormous white chedi, topped in gold, is said to hold a relic of the Buddha, and it is a pilgrimage site of real weight in southern Thailand — sitting on the country's UNESCO tentative list. It is a working temple full of Thai worshippers rather than a monument staffed for tourists, which is the whole difference.
The province behind it runs from the Gulf coast up into the Khao Luang range, whose namesake peak is the highest in southern Thailand. That means cloud forest, waterfalls and fruit orchards — mangosteen and durian country — an hour from beaches that see almost no foreign visitors.
The city is also the home of nang talung, southern Thai shadow puppetry, still performed and still taught here; the Suchart Subsin puppet house is the best-known workshop.
What this is not is convenient. The province rewards a car and a few days, and gives very little to someone changing buses.
02How to experience it
Fly from Bangkok or take the southern line. Hire a car — this is the one piece of advice everyone who recommends the region attaches. Give the temple a proper morning, then head inland for Khao Luang's waterfalls, and spend an afternoon at a puppet workshop. Pair with Khanom up the coast for pink dolphins if you have a spare day.
The honest note
You need a car, and people say so unprompted. From someone naming this stretch as their favourite part of Thailand: "Very under touristed because truthfully to see the best of it you need a car, and largely the experience is mostly nature/restaura[nts]." Without one you will see the temple and little else.
The rain is serious and badly timed for most itineraries. This is the Gulf coast, so the monsoon arrives October to December — the exact months many people visit Thailand.
There is little English and little tourist infrastructure. That is the appeal and the friction in one sentence.
The province appears in Thai news for gun crime, which is worth knowing and worth keeping in proportion: it is a domestic-violence and feud pattern, not something aimed at visitors, and nothing in the corpus suggests travellers are affected.
From the locals
Asked for the most underrated place to visit in Thailand, one answer names the province and then lists why in a single breath: "For me personally Nakhon Si Thammarat. It has everything, jungle, mountains, beaches, fruit farms, one of if not the most revered buddhist temple in Thailand and so on but it's less developed around international tourists so travel inside the provinc[e]…"
In a thread titled, simply, "The hidden gem of Thailand", someone else drew the boundaries of the same region: "The region from Chumphon down to Nakhon Si Thammarat is my favourite part of the country. Mostly the countryside areas."
And it appears on the corrective list given to a traveller who complained that Thailand had disappointed them — the reply pointed out they had "quite literally traveled to the major tourist spots" and offered provinces instead: "Chumphon, Ubon Ratchatani, Loei, Nan, Chiang Rai (less touristy than Chiang Mai), Nakhon Si Thammarat, Kang Krachan Natio[nal Park]."