Thanks all for the tips. Much appreciated!
As I've mentioned, my friends are not sexpats, they're young professionals, so no need for the gogo bars. They want to explore a city, a beach and some mountains, so it will be Bkk, Pattaya and CM. They've already booked the flight to Bkk.
Re: Pattaya, I've heard your advice and will lead them to Pattaya Central or Koh Larn (up to them).
Re: CM, whether train or plane - up to them, depends on their time & budget. Where is it better to stay in CM, Old or New City? They'll want to see a temple or two.
@Bogon - I've read your bogon tips, gracias!
Are there trekking/hiking trails in CM? How far (in hours) are the Doi Inthanon and Op Luang National Parks?
Thanks very much!