Century Eggs, or ไข่เยี่ยวม้า (khai yiao ma) in Thai, are not extremely popular in Thailand, but they can be found in some Chinese restaurants and markets, particularly in areas with a large Chinese community. I've just been served some with a Thai dish or fried basil and chicken over rice. 

The name "horse piss eggs" is believed to refer to the dark color of the eggs, which resembles the color of horse piss. Anyone care for some?

2 hours ago, Palatus said:

The name "horse piss eggs" is believed to refer to the dark color of the eggs, which resembles the color of horse piss. Anyone care for some?

 

Don't think so.  There's an urban legend that the eggs were originally preserved in horse urine, but that's unlikely.  Horse urine is not normally dark.  It's much more likely that the name arose because they smell like horse urine because the preservation process produces hydrogen sulphide and ammonia.