hi Sophie, im currently travelling atm and doing almost the same route as what your planning. at the moment im in malaysia.
when you're flying into bangkok would you not want to go cambodia, vietnam and laos as well as thailand? i could have easily spent 1 and a half months doing thailand alone, ive had 3 months in asia now and just finishing up. but if you just want to do thailand then a month is good. maybe add on 8 days for malaysia. stop off at kuala lumpur then head down to singapore for about 4-5 days. (just come from there, its great fun!)
2-3 months just doing the east coast? im doing the east coast in 5 weeks. i think 1 and a half months would be a good time. depends on how many places you want to stop off at...
your budget is going to be more than that for your ticket. my RTW that i bought in May of 2010 was £1700 and that went from Heathrow to Bangkok. Hong Kong to Cairns. Melbourne to Fiji. Fiji to Hawaii. Hawaii to LA. La to Healthrow. if i would have added in NZ i think it would have bumped the price up quite a bit more. however STA travel are having a sale on atm, get yourself to their website!
the answer to question 3 depends on what type of ticket you get.a RTW ticket you need certain dates to travel on. if you change those flights you have to pay a fee.
answer to question 4 is easy. you dont have to fly everywhere. my ticket at the start was from heathrow to Bangkok. my next flight on my RTW ticket is from Hong Kong to Cairns. so since i landed in bangkok ive gone through cambodia, laso, vietnam, thailand, malaysia and singapore. im getting a small flight which IS NOT included in the RTW ticket from kuala lumpur to Hong Kong where i will stya for a week then get on my RTW ticket flight to Cairns. (i hope that made sense!)
any questions? hahaha