We are considering a trip this summer. We've used Sunsail twice (and they have a marina there) but would consider other options that are reputable. We would need a 38 foot catamaran for my family of 4. Thanks in advance for your recommendations!
we chartered a Wharram Tiki from Siam Sailing- small operation run by an old Dutch salt who was incredibly helpful and laid back. We chartered the 30 footer which was basically like a hobie cat with a bit of a cutty cabin- perfect for the two of us, but you'd need one of their 38 footers. they were significantly cheaper than the typical charter. we went in May/June so given the winds we stayed up in the bay. good luck!
Elite yachting is probably the best company for you. They have a couple of newer lagoon 38s and Lagoon 400's. Well maintained and clean. Another company couple of companies you could have a look at are Moorings and Simpson marine. These two will be a little more expensive than Elite Yachting. Best to book early as cats in Phuket are in high demand.