I'm in Thailand as part of a cruise next Jan/Feb, if we like it (never been before) me and Mrs H are looking to do three weeks there in Feb 26, I've done a comparison (using this Februarys prices) on costs between going to Thailand and one of the Canary isles.
Tenerife
Flights, including seat allocation and luggage, £500
Apartment with Kitchen decent 4 star plus rating for 21 days, in a coastal resort south of the Island, £2000
Living money based on our lifestyle £2500
Total: £5k
Phuket: same criteria
Flights, £1400
Accommodation £1000
Living money £1400
Total £3800
No brainer really, better climate, much better value for money.