Thailand forum

birdie,

how much time will you have for your island portion of your trip, and what is your budget?

also, keep in mind that mid-april, particularly the 13th through the 15th, is the new year/songran holiday, so you'll need to have your accomodation and transport sorted ahead of time if you are travelling over those days.

Only 1 week is really pushing it. If you desperately want to go south, you'd have to fly, so to avoid a lot of travelling from the airport you've realistically only got the choice of Samui or Phuket, or if you're really well organised Railay Beach or Kho Lanta. Not sure if Khao Lak is back to normal, though that would be an option from Phuket airport.
Much simpler to stick closer to Bangkok, which basically means Kho Samet or Kho Chang. Though it's not on an island, Hua Hin is definitely relaxing, with nice long beach walks.
Consider River Kwai area for some very nice resorts, if relaxing is your primary objective.
If you've never been to Thailand before, you might want to return to Bangkok at least 1 day before outward flight in case of ( not uncommon ) travel delay.

I would like to get from Ko Samui across to Ko Lanta - any ideas on the quickest or cheapest way of doing that?

I went to Koh Chang the end of June (rainy!) also because of a time issue, and suggest that if you do go there you go toward the southwestern part of the island (Lonely Beach). Although there is a lot of construction beginning (won't go back in a couple years!) it is a much less touristy and beautiful. I stayed at The Nature's Resort and it was great. The bungalow was nice, the swimming was great (nice waves), and the restaurant area was comfortable with pillows and hammocks and good food.