This is another listed by the folks who present The Caves of Thailand, the website has the most complete list of caves of Thailand I have ever seen. In most countries the tourism board is usually the place you can find that kind of imformation, but here in Thailand the Tourism Authority of Thailand is the last place to look for information. In the video linked here on youtube. There would be a public outcry if it was thought the women in the shorts was a Westerners dressed inappropriately for a religious site, but Thais routinaly dress like this and nothing is said.If you are on the river road between Nong Khai town and Sangkom there are a few interesting stops. You might need to click on view in larger map as the icons sometimes do not open
Below youwill find the info provided by the folks linked about and a Google map section..
HISTORY: Wat Tham Si Mongkhon or Wat Tham Phiang Din is the 38th temple of amphoe Sangkhom. It was built in 1938 by Luangphu Hom who stayed here as a monk on austere practices. Luangpu Sang came to stay at this temple in 1947. In 1960 Luangpu Song arrived here and joined the building of a preaching hall. Later more buildings and monk cells were established. At present the temple covers an area of 150 rai having nine monks and two novices. The most important place in this temple is Tham Phiang Din, the cave which the temple is named after. It has been told for generations that the cave was a channel used by a monk on pilgrimage from Laos to come here without crossing the border by boat. Only virtuous men or noble monks could see the path in the cave. Later, the cave was discovered by a hunter who chased his prey to this cave and entered the cave through its tiny entrance. The cave was similar to the underwater world of nagas (mythical serpent) according to the belief of the villagers. According
POSITION: Wat Tham Si Mongkhon is signed to the south of the H211. A good road, with frequent signs including English ones, goes for 20 km to Ban Dong Tong and then on to the large wat.
DESCRIPTION: A stream sinks into the sandstone below the large Buddha. A few metres away is a naga shrine and some steps lead down into the small entrance. After a narrow, triangular section with knee deep water the cave opens out into a small chamber. Off from the chamber is a maze with every joint eroded every couple of metres. The roof and floor are of a different, harder sandstone and the passages are about 1.5m high. The stream passage was has not been followed to a conclusion as it lowers to a crawl with bats flying out, but the resurgence is only 200m away. The guided tour goes out of the cave following a different stream passage.
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