What exactly are you looking to trade? If you want to trade US stocks, there are many many brokers you can open an account with. If you like TDA, just ask them with one of those online chat with agents. I personally like interactive brokers as their commission is much cheaper for trading 100-500share lots. But they do require much more than $500 to open an account.
If you are looking to day trade stocks, US stocks won't be a good idea from your location unless you are a night owl. Plus you do need to fufill PDT rule. Otherwise, 3 roundturns max per week as mentioned.
Korean stock market doesnt have a PDT rule, and should be easier for you to start with. Plus their commissions are percentage based at say .005% or something like that. Much cheaper for small accounts to trade. I hate their platforms though.
Best of luck.
Can't open an IB stock account with $500...