This is a travel video from mickspatz recording the trip to a Natural Attraction of Thailand at the Mekong River:
"Sam Pan Bok (from Thai: สามพันโบก) is known as the Grand Canyon of Thailand and has the biggest rock reef in the Mae Khong River.  In English "Sam Pan Bok", means 3,000 holes. Sam Pan Bok is located in the East of Thailand, near Mae Khong River in the Laos border. Ubon Ratchathani province.The Tourism Authority of Thailand (TAT) classified it as one of the tourist attractions of "12-month 7 star 9 sun, amazing Thailand that must be experienced."
In addition, Sam Pan Bok resembles very large rocks like the mountains in the middle of the Mae Khong River. The beautiful rock holes were caused by the rushing water. Some are big enough for people to get through and some are small. The rock holes are scattered all over the place in different shapes and many other imagined things (extract from Wikipedia).