Newnewnewbie to backpacking! From Singapore!

Hello there! I'm Sarah from Singapore. I've always wanted to backpack around and in a few months time I'm turning 18 so I want to do something really different during my semester break. I was planning to just have a short getaway but in a backpacking way to the neighbouring country either Malaysia, Perhentian Islands or Thailand, Khrabi.
I only have a budget of 800SGD (635USD) to spare from air tickets to hostels.
And I have no idea which is the better choice.

Apart from that, my parents aren't approving of me to go overseas alone, and how do I convince them that I'll be fine and okay.

Thank you!

Cheers,
Sarah

Please note that this site is about North American style "backpacking," which is wilderness trekking, not about budget travel.

There are a number of budget travel forums on the net, such as Lonely Planet, although that site isn't as good as it used to be. I suggest you try those.