The City of Angels
Bangkok can be a very cheap destination but it also can be very expensive depending on the luxuries that you wish for. You could eat all day and night, have a few beers in a bar and visit some tourist sights all for under £10. On the other hand you could spend the day in a luxury spa, sip champagne on top of skyscraper and travel around in a private limousine for a much more expensive price.
As a visitor, accommodation is going to be your biggest expense, costing anywhere between £4 in a Khao San Road hotel and £1000 for a luxury double room in one of many 5-star hotels. Costs of accommodation and travel can depend on high season/low season issues so check before travelling. The cost of shopping in Bangkok depends whether you purchase items in one of the many street markets or in one of the climate controlled mega malls. In some shopping malls VAT can be refunded on goods bought in Thailand when leaving the country.