A young bull poses for his portrait, in Sisaket.

Isaan rice field

Rice harvester, lower Isaan

The crop is in and the harvested stalks gathered for feed for livestock.

Harvested field in early-morning light

A vast, flooded landscape at Rasi Salai after the Mun River overflowed its banks during the rainy season

A fisherman takes advantage of the newly-formed 'lake' at Rasi Salai.

View at Pha Mo I Daeng, above the border with Cambodia in the southeast corner of Isaan. The controversial Khmer temple ruins seen in the background, Prasat Preah Vihear—Khao Phra Viharn in Thailand—were somehow ruled by a world court to be on Cambodian territory.

The Huai Luang Waterfall at Phu Chong Na Yoi, in the extreme southeast corner of Isaan near the borders of Laos and Cambodia

Near the base of the waterfall

Forested hillside at Phu Chong

Below the falls

Huai Luang Waterfall from below

The top of the waterfall

Huai Luang

Huai Luang Waterfall

Across lower Isaan and well away from Phu Chong Na Yoi National Park is Thailand's oldest national park, Khao Yai, an 840-square-mile sanctuary in the southwest corner of Isaan. Seen in the photo is the park's Haew Suwat Waterfall.

Roots and stream, Khao Yai National Park

Barking deer, Khao Yai National Park. They are so named because their call resembles a dog's bark.

Stream along a trail leading to Khao Yai's Pa Kuay Mai waterfall

Some 2,000 species of plant life are found within Khao Yai's five main vegetation zones, which range from the lower slopes to the tops of its mountainous terrain.

Phu Pha Man National Park straddles parts of districts in both Loei and Khon Kaen provinces, northern and central Isaan. Its limestone mountains and junglelike mixed forest cover nearly 219,000 rai (over 86,000 acres). There are several caves containing beautiful stalactites, stalagmites, and stone pillars.

Cassava field, north-central Isaan, with rice and corn fields in the distance. Cassava can grow year round in infertile soil, making it well suited for cultivation in Isaan. It is raised for its edible starchy root and as a source of tapioca. Cassava chips are also used in biofuel.

Loei Province. As one travels farther north across Isaan's Khorat Plateau, the flat landscape of the southern region increasingly gives way to rolling hills and mountainous terrain, with the higher altitudes making for cooler weather conditions as well.

Mountainous landscape in Loei Province

The Siam tulip (Curcuma alismatifolia) thrives in northern Isaan, where it is called bua sawan, “heavenly lotus.” The common names notwithstanding, it is neither a tulip nor a lotus but a member of the ginger family.

A patchwork of rice fields viewed from a mountainside in Loei Province, northern Isaan

Kaeng Song Khon Falls, Loei Province

Rolling hillsides in Loei Province, northern Isaan

Pla Ba Waterfall, Loei Province

Rainy-season landscape at Dansai, Loei Province, northern Isaan

A view from the top of 4,511-foot Phu Rua, Phua Rua National Park, Loei Province

At the top of Phu Rua, one of the coolest spots in Thailand, where the temperature can plunge to freezing levels and below in the winter

From the top of Phu Rua

Vegetation in the park ranges from that of grasslands to tropical, evergreen, and pine forests.

At the top of Phu Rua

Phu Rua

Early-morning fishermen on the Mekong River at Chiang Khan in the extreme north of Isaan, with Laos across the river in the background

Fog-engulfed landscape at dawn along the Mekong at Chiang Khan

More fishermen at dawn on the Mekong at Chiang Khan

Fishermen in the early-morning light

The Mekong at Chiang Khan as daylight begins to fade

Boats moored at a landing in Chiang Khan at the end of the day

A spectacular twilight display in the sky over Laos, seen from Chiang Khan. The Mekong forms the border between Thailand and Laos, beginning in the north near Chiang Khan.

Darkness settles in quickly over the Mekong at Chiang Khan, but the sky retains its impressive spectacle as night closes in.