Nayang cave in Thailand is famous for it's colony of wrinkle-lipped bats but I wouldn't recommend it as a place to experience bats actually in the cave itself - the bats are out of sight high-up, the place has a very strong guano smell and it's crawling with 'roaches. None of which come over well on social media! However, there is another cave about 3 kilometres south-east that does offer a decent bat cave experience for the reasonably fit and mildly adventurous.
It's at Tam Khao Tachin, which is in Petchaburi Province at the north end of the Thai peninsular. It feels like a temple but isn't actually called one. From the buildings there is a steep but short staired path up the hill to the cave entrance. There are lights inside but they are only switched on if you ask. I recommend taking your own torch/flashlight instead to minimize disturbance to the resident bats.
The first bats you find will be black-bearded tomb bats (𝑇𝑎𝑝ℎ𝑜𝑧𝑜𝑢𝑠 𝑚𝑒𝑙𝑎𝑛𝑜𝑝𝑜𝑔𝑜𝑛) - this is actually true in most caves in Thailand. For bats, they make quite a pleasant chirping sound. There are a few hundred of them in groups dotted around with the best view usually being up a cleft on the lefthand side just after you pass the cave's Buddha statue. They have pleasant pointed faces and a nice demeanor.
That's the easy bit done. After this you will need to step carefully and do a bit of clambering so outdoor footwear with good grip is advisable. There are a few possible routes to head and it can look confusing but the cave is not really deep enough to get properly lost in - however, the risk of torch/flashlight failure is something to be wary of so I recommend always taking a backup light and a sensible friend. I also wouldn't recommend taking children further than where you can see the tomb bats.
Without having to go much more than 20-30 metres further you will probably find the other bat species common in this cave. Some will be flying around but you should also notice lots of loose groups of various roundleaf bats hanging openly on the cave walls as they don't bunch together like many bats do. The commonest are long-eared roundleaf bats (𝐻𝑖𝑝𝑝𝑜𝑠𝑖𝑑𝑒𝑟𝑜𝑠 𝑝𝑜𝑚𝑜𝑛𝑎), which are lovely if you can get a good view with their small faces and big ears rotating around. The larger ones are not quite so cute and there are three species of them in this cave (𝐻𝑖𝑝𝑝𝑜𝑠𝑖𝑑𝑒𝑟𝑜𝑠 𝑙𝑎𝑟𝑣𝑎𝑡𝑢𝑠, 𝑙𝑒𝑘𝑎𝑔𝑢𝑙𝑖 and 𝑎𝑟𝑚𝑖𝑔𝑒𝑟). Interestingly, most of these larger roundleaf bats disappear for a few months in the dry season (Dec-Mar). I have no idea where they go.
Except for a very rapid clicking/chittering sound, the roundleaf bats are also relatively quiet, which helps with finding the smallest species. The Himalayan whiskered bats (𝑀𝑦𝑜𝑡𝑖𝑠 𝑠𝑖𝑙𝑖𝑔𝑜𝑟𝑒𝑛𝑠𝑖𝑠) like packing themselves tightly together in cracks and crevices. This makes them harder to find but they are also quite noisy and their batty chattering screeches are the best way to find them. Sometimes they are tucked away quite well hidden, sometimes they are more out in the open. Luck of the draw.
There are a few horseshoe bats (𝑅ℎ𝑖𝑛𝑜𝑙𝑜𝑝ℎ𝑢𝑠 sp.) in this cave but they are hard to pick out from the other smallish bats.
In total I'd guess there are several thousand bats in this cave of at least seven different species and if you venture a short way down one of the narrow passages you will experience some of them flying very close to you. This cave offers a great feeling of being in a real bat cave without the atmosphere being too intense.
Finally, on the way out pause to enjoy the view from the cave mouth. You can see the northern part of Cha'am plus have a lovely view of the shapely limestone hills of Khao Nang Panthurat surrounded by flat paddy-fields.
Please note that this site always closes its gate by 5pm so if you go be respectful and don't make them wait for you! It does make a good additional trip on the way to watching Nayang's wrinkle-lipped bats if you don't mind having a longer than usual wait at the viewing platform.
Good batting!
Bats of Nayang Facebook Page has more info about bats in the area