Just to expand slightly, all mobile phones in Thailand have the following 10-digit number scheme:

08n nnn nnnn

(The second digit of "8", following the leading zero, was added ~ 1 year ago to all exisiting and newly issued mobile phone numbers, hence the omission.)



Fixed lines also have a similar "leading zero":

Bangkok/environs: 02 nnn nnnn (9-digits)

Other provinces have a 3 digit prefix followed by a 6-digit phone number:

03n nnn nnn / 04n nnn nnn / 05n nnn nnn / 07n nnn nnn

example: Chiang Mai: 052 nnn nnn; Phuket: 076 nnn nnn; Krabi: 075 nnn nnn

I think Koh Yao would have a 076 prefix for fixed lines?

In country calling you use the leading zero to either/both fixed and mobile numbers, calling into Thailand you drop the leading zero, so this gets represented as (0). The country code for Thailand is 66. In many countries you use "+" to access international trunks. In the U.S.A. some carriers allow the use of "+", but most require "011".