Her Royal Highness Princess Maha Chakri Sirindhorn Herb Garden

Her Royal Highness Princess Maha Chakri Sirindhorn Herb Garden opened as Thailand’s first dedicated herb garden in 1984, built by PTT and presented to the Princess on 18 April 1985. More than 260 herb species — over 20,000 individual plants — grow across the grounds in Nikhom Phatthana district, Rayong, grouped into 20 categories by traditional medicinal use: blood tonics, skin remedies, aromatic herbs, and plants historically used against cancer among them. Entry and the guided tour are both free; the garden is open Tuesday to Sunday, 09:00–16:30, closed Mondays.

Visitors register at the PR point near the entrance, then join a tour by bicycle or NGV cart with a guide who explains what each grouping treats and why — details easy to miss reading the planting labels alone. Carts depart roughly every 30 minutes between opening and 16:30. The commemorative building marking the Princess’s 50th birthday houses interactive exhibits on herbal medicine, and the grounds also hold food stalls, a shop selling herbal health products, and a Thai massage pavilion for anyone wanting to sit out the heat.

Insider Tip: Ask for the NGV-cart tour rather than walking it alone — it’s included free, and the driver-guide’s running commentary on which plants treat which ailments is most of the value here; the labels alone don’t tell that story.

Mornings are quieter and cooler for the tour, and the garden reads more like a working botanical collection than a manicured show garden — shaded paths, working plots, and a pace that suits an hour or two rather than a half-day.

Watch out: The guided carts run on a fixed half-hourly schedule rather than on demand, so budget a short wait if you arrive between departures — and remember it’s closed Mondays, unlike most other Rayong stops.

The garden sits on about 60 rai within a PTT residential compound at Ban Tha Dan, with enough tree cover across the paths to keep the tour comfortable even at midday; PTT marked the garden’s 40th anniversary in 2025, still promoting it as the company’s flagship public heritage site in Rayong. Groups should call ahead to the PR Department (0 3891 5213-5) rather than arriving unannounced; PTT’s own site (pttplc.com) carries basic visitor information. Pair a visit with the Rayong Agriculture Promotion and Development Center, a similar hands-on agricultural-education stop north of Nikhom Phatthana.