Hi and welcome to the forum. This is actually the Bali subforum, but never mind - your query is quite general so it fits in here OK
Check the PayPal buyer protection policies; generally they'll have your back if things go south. But to be doubly sure, what I would suggest you do is ask them to send you a PayPal invoice for the amount you need to pay. When it arrives in your inbox, check it's legit and that it actually goes to a page on the PayPal site (you can't be too careful). If it checks out, then you can usually either pay with an existing PayPal balance (you log in etc and then pay) OR you can (usually) pay with a credit card. Do the latter - pay with your AMEX or Visa - and then you will be doubly safe as credit cards tend to have a whole range of buyer protection/insurance benefits as well (but check your card to be sure).
Basically, everything will probably work out OK if you proceed with the booking (they might hold back the deposit if you cancel - that should be in their terms and conditions), but if you've got PayPal and AMEX or Visa behind you, you should be fine in theory.
I am sure you know this, but for the benefit of anyone else reading - DO NOT pay these kinds of deposits directly into bank accounts or via Western Union. These methods offer ZERO protection if things go south! Stick to PayPal or other payment methods with strong consumer guarantees.
Enjoy your trip