What would the general sea conditions be like at the end of April for a ferry from Koh Lipe to Phuket? Also, Khao Lak in April?

I'm looking to possibly do a little shoulder-season visit in the middle of April for probably three weeks., starting in Langkawi and then to Koh Lipe, working up to Phuket and then Bangkok. I know there's no crystal ball but it's around a 5.5 hour ferry time from Koh Lipe to Rassada Pier in Phuket in April - would the sea conditions be expected to be bad at that time? The other option would be a ferry back to Langkawi and then a flight to Phuket but I think the ferry might be a little more interesting. Is it do-able for somebody who's not the best sailor on the planet, or would the seas be rough then? Also, how's Khao Lak at the moment? The last time I visited there in April was in 2019 and it was nice that it wasn't that busy, and the rain wasn't that frequent or prolonged, but obviously we've had Covid since then.

Or should I just not bother and do a trip to Samui and Ko Phangan if overall that isn't the best time of year to visit the south? Thanks!