Going Overseas for awhile and I need a Phone....what should I get???

[SuikodenII]

From my own independent research I'm hearing I should get an unlocked T-Mobile phone, then I saw this...

http://www.worldtimezone.com/gsm.html

I'll be going to either China, South Korea or Japan and I'm not sure how to read the chart on what I would need



Any help is appreciated