Nong Khai (เทศบาลเมืองหนองคาย, Thesaban Mueang Nong Khai (Nong Khai Town) or หนองคาย or Nong Khai) is a city in north-east Thailand. It is the capital of Nong Khai Province. Nong Khai city is administered as Amphoe Mueang Nong Khai.
Nong Khai lies on the Mekong River, near the site of the first Thai-Lao Friendship Bridge, spanning the river to Laos. The Thai-Lao Friendship bridge was largely funded by a gift to the Lao government from the Australian government. It is the road and railway gateway to Laos's capital, Vientiane, 25 kilometers upriver, on the north bank opposite the Thai town of Sri Chiang Mai. Construction of a rail spur to Thanaleng outside of Vientiane was begun early-2007 and officially opened 5 March 2009.
Nong Khai is 626 km north of Bangkok and 60 km north of Udon Thani.
The Prap Ho Monument before the old city hall (now a museum and cultural center) memorialises the dead of the Haw wars.
In more recent years, Nong Khai has become a popular destination during the Buddhist Lent festival when mysterious balls of light, or Naga fireballs, rise from the Mekong River. The balls resemble an orange sun. They rise out of the river approximately 6–9 meters (20 to 30 feet) and disappear after three to five seconds. Although the fireballs can be seen at other times, most Thais travel to see them during the full moon in October when the incidence of them is considered to be much higher.
Nong Khai's main sight is Sala Keoku (alternatively spelled as Sala Kaew Ku, also known as Wat Khaek), a park of colossal sculptures, some over 20 m tall. The park is the handiwork of the mystic Luang Pu Bunleua Sulilat, who bought the land in 1978 when he was exiled from his native Laos, where he had built a similar park in Vientiane in the 1950s. Synthesizing Buddhist and Hinduist ideologies, Buddhas, many-armed goddesses, a seven-headed Naga snake, and various human-animal hybrids dominate the site.