Which hotel would you choose if you're a single female traveller.?

Yes, agree with Holiday Inn Bangkok. It's new and modern one. Staffs are nice and friendly. Though it's located in CBD of Bangkok, it's quite safe and not noisy 'cause it's no street vendor and tout in front of the hotel. There're BTS station(Chidlom), Gaysorn Plaza, Amarin Plaza and Erawan Bangkok close to the hotel. Central World is nearby (within 10 minute walking). They use Red Earth for toiletries, same as Holiday Inn Phuket (I love it). Enjoy your trip :)