One important thing to realize is that all the companies you want to audition for are Korean companies. That being said, it is obvious that they are going to try and appeal to the Korean public and the best way to do that would be through Korean people (do you see where I'm going with this.)

Now that's not say that companies are against foreign potentials. Quite the opposite actually since now, most companies would want to globalize their groups (being global brings in more money anyways) so foreign audtioners, especially of Chinese or Japanese (but more Chinese though as there is this huge political rivalry thing going on between Korea and Japan and also because of WWII, in which case China also has bitter settlements against the Japanese) descent.

Now those that are from South East Asia, don't be discouraged quite yet. We can see that Nichkhun is Thai and there is a new YG trainee (Lalisa Manoban, I think) who also hails from Thailand and many members of Skarf who are from Singapore. The market is slowly becoming more open to South Eastern potentials as companies see a huge marketing possibility in those areas. However, it is important to note that Nichkhun, Skarf and Lalisa don't really look South Eastern, they look like they could be Chinese, Japanese, and/or Korean. This mostly has to do with a huge cultural belief they have in Korea -- as they often times look down on South Eastern Asians.

For all of you Chinese (or maybe Japanese as well) potentials out there, you would be happy to hear that many companies now see a HUGE marketing possibility in China (or maybe Japan as well but then again, theres that whole controversy surrounding the two nations).

But, that's not to say that you can't be the first one! Look at Hangeng, who was the first Chinese to be in the South Korean market or Olivia from the Gloss who is, dare I say, is European. You could be the first FILIPINO in the market, you never know 

If you were to take one thing from this, it should be:

tl;dr You are extremely advantaged if you are Korean. Then Chinese. Then Japanese. Then anyone who looks like they could be any of the ethnicities I just listed. Anyone else, I'm sorry but you don't have a good chance if you aren't any of that I mentioned above. Its the sad reality of the entertainment world and its best if you realized that now than later.