Everyones' budget will be different depending on circumstances...like if you're single or travelling with a partner/family...and also on what your interests are.
For anyone travelling single, this will give you an idea of DAILY expenses based on a fairly typical day for me.
Room...........400
I'll rent an apartment for 12000 a month...can get cheaper but I like comforts, quiet and a nice view :-)
Motorbike+Gas.....140
3500 a month and costs 60baht per tank of gas...I use 2 or 3 tankfulls a week as most days I go off to one of the other beaches.
Beach sunbed.....50
Drinks+fruit at the beach.....100
Beach restaurant...Beef in Oyster sauce with Steam Rice :-)...80
Oil massage in Patong....300 + 50baht tip....350
Internet.........40 I'm usually on for an hour or so per day
Restocking fridge with drinks/yoghurts.....100
Evening food....200 includes usually visiting a noodle soup cart at 2 or 3 in the morning!
5 games Pool.....100
Nighttime drinks.....1000+ Can vary tremendously depending if I drink local brews (trouble is I like Jack Daniels too much) and how many lady drinks I buy.
Lady...........1200 Bar fine and gift for lady if I want some "no strings company"!
Total daily expenses.....3760 baht
Hmmm, so if I was frugal and stayed in the apartment at night I could live on less than £25 a day
http://www.bbc.co.uk/guernsey/features/asian_tsunami/index.shtml
Patong Beach