Ah yeah as far as Thailand goes they're the pricier end but still very cheap. Bangkok is the cheapest out of those, you can get amazing Street food for like £1 and a decent dinner in a restaurant for £3-4. Beer is about 80p. Samui and Phuket a bit more as they're aimed more at tourists, but still a good meal for a fiver, beer like £1. Some of the more touristy bars more like £2 for beer. Boat trips are a little bit more, probably doing watersports is the most expensive thing you'll do there. If you are just looking to chill, drinks and eat and party you could easily get by on £30 budget a day. add a bit more if you wanna do loads to activities like boat trips, snorkeling trips, parasailing, etc, boat trips vary between maybe £20 and £60 depending how extravagent.