World's top 5?

Inner Mongolia (or Nei Mongol) is another of the huge automonous regions of China. Inner Mongolia borders Mongolia, to the west of Beijing. H

In the regions capital Hohhot one can stay at the Water Moon Hotspring hotel, tripadvisor states, though I'm not totally certain whether or not that really is the case.

World famous Wiener
Apparently it was once stated on internet that once used to state:

'There are many hot springs in Inner Mongolia, including the world famous five'.

However, whether this info is now considered useless or whether it's just a case of the internet evolving in directions unknown it remains a question. However if true, the hot spring named Wiener Creek is just one of those 5. The Chinatravel website used to add to the above sentence:

'Located in the middle of Xilu Wei Nahan Daxinganling mountains mountains in the Wiener River mineral field, there are seven springs arranged in the context of more than ten square meters, and some very clear and clean spring water, some were white, some brown-yellow, water temperature were 2 ° ~ 6 ° C, the water quality with world-famous French spa Vichy comparable. They generate strong in much of ancient Tertiary volcanic activity, was Mongolia, Oroqen, Ewenki called “Shen Shui.” Have been developed using universal spring, spring stomach, acid springs, the heart of spring (above 4 springs for drinking spring), the first spring, ear, nose spring, seven medicinal springs bathing spring, about 40 tons per day and night flow can be bath treatment for 45 thousand people used to drink. Mineral water contains more than 230 kinds of minerals, on dozens of chronic diseases have a significant effect'.

Natgeo
The UNESCO designated Hexigten National Geopark contains the Reshuitang thermal spring, another of the mentioned 'world famous five' as well as a number of other geological phenomena. 
Reshuitang is located 30 km north of Jingpeng. Jingpeng is the site of a famous railway pass. According to tripadvisor there is a hotel named Yangguan Hot Spring Hotel. 
More on Reshui can be found here including this last sentence:

'At present, there have been 10 hot spring sanatoriums. This hot spring town which is beside the mountain and water has beautiful scenes'.

This website adds:

'The hot spring was developed 1.000 years ago.In the Liao Dynasty Emperor Taizong and his successors had baths in the spring water In 1686, Emperor Kangxi of the Qing Dynasty visited the hot spring and took a bath. The site where the Qing emperor bathed remains today'.

Visitors though might want to look up the info on tripadvisor. As this recent poster experiences:

'Unfortunately the hot springs in the town square have been closed for many years and the hot springs in a big hotel with a hot swimming pool were also closed.

...

The huge stone at the entrance of the town announced that this town is famous for hot springs, but no hot springs were open, apparently they only open in May. So don't go there before May, at least I could find a hotel with hot baths, so that was my hot springs experience!! '

More fame
On Ning hot spring, another of those famous 5, there is nothing additional mentioned.

On the hot spring of Liangcheng located near Daihai Lake, Liangcheng county

'Located in the mountains of central Inner Mongolia, Han Liangcheng Daihai very hot, because legend of Emperor Kangxi, when the patrol side spring mount thirst in this plane, also known as “spring plow horse,” Temple has been built Yongxiang, aristocrats, celebrities Ascot and the monk Lama bathing resort of convalescence. Underground water is a sodium bicarbonate-based weak mineralization of water, water temperature 37 ° ~ 38 ° C, rich in lithium, zinc, strontium, radium, metasilicate, selenium, iron, magnesium, sulfur and other chemical elements and minerals substances, rheumatism, rheumatoid, skin diseases, low back pain, dry skin and other diseases have a significant effect'. source

Apparently there's now a hotel named Daihai Hot Spring Hotel. What can one expect? 

'Daihai Tourist Area is mainly composed of three parts - Daihai Hot Spring Resort, Daihai Tourist Resort and Daihai Hot Spring Hotel. In recent years, great investment has been made on the Daihai Scenic Area. It has built several hotels, Daihai Tourist Center, Daihai Spa City, Daihai Ski Resort and Daihai Cultural Tourism School and other projects. Now the 130 square km area around Daihai Lake is a suitable place for leisure, conference and sightseeing.
Daihai Hot Spring Resort( or Daihai Spa City) is just 500meters north of Daihai Hot Spring Hotel, about 10km in the west of Liangcheng County. The Daihai Hot Spring Resort is a Japanese style garden building with 4 indoor hot spring pools. The Daihai Spa City is located at the foot of Manhan Mountain with plentiful hot spring resources. The hot spring temperature is mild and comfortable ranging from 40 degrees to 60 degrees. There are 17 kinds of minor elements in the hot spring water. It is good for the treatment of the pain in low back and legs with rheumatism. The Daihai Hot Spring is often regarded as "Holy Hot Spring Beyond the Great Wall".

The accompanying photo's though reveal a rather dour inside soaking area with yes a fake Japanese touch. This blogger has visited here and leaves this strange comment:

'Otherwise I loved Liangcheng (well one of the small villages surrounding area): we stayed in a Japanese style hotel with its hot springs, almost every family has its own dairy cow, and it’s incredibly easy!'

And a top ski
Arxan (Aershan) is the most mentioned hot spring in Inner Mongolia. Better known for it's ski area (see Ten Best Places for Skiing in China), Arxan is apparently also home to a hot spring museum. I'm not totally sure if this is what a museum means:

'The museum will feature different sites including the Arxan hot springs, volcanoes, as well as bizarre lakes and stones.

The museum locates outside Arxan city, a Chinese frontier town southwest to Daxinganling Region, the city boasts the largest and best-kept volcano basalt physiognomy and the world's largest hot springs used for drinking and bathing.

One of the area's most spectacular sites is a concentration of 48 hot springs that are classified into three different types and four different temperature levels'.(source)

Another aspect that makes Arxan hot springs famous are that it is the largest group of radon hot springs in China (source, link not functional). It is also noted that the local stream is ice-free during winter (source).

Despite all the factual claims to fame there seems precious little photographic evidence of any soaking available. A couple of indoor sites fake Japanese style. One going by the name Haishen Hotspring Hotel (located on Hotspring street). Though this seems attractive enough:

Arxan seems a great place to do nothing:

'AereShan is a famous Mongolian hot Springs area. There is a hot spring for every body organ. The area is all beautiful mountains. We went for a drive into the mountains and wow. Wild flowers. Rivers. Mountains. There is not much to see in the town, so this is an area to relax, use the hot springs, and learn the history'.

That description seems quite compelling. Whether or not this will remain is possible not the case. A recent news article suggested that Aershan will be the focus of Sino-Icelandic geothermal investment.