Koh Chang to Phuket / Utapao - How?

Hi,

i´m new to this forum (but going to Thailand since 30 years, so i´m not new to Pattaya...)

I have a question that google unfortunately cannot help, so maybe somebody here have the answer:

I want to travel Koh Chang to Phuket, without staying overnight in Pattaya or Bangkok.

So my questions are:

1.) The cheapest way is to book a flight via BKK and take this (well known)  "big bus" (starting at BKK airport, downstairs). You pay 600.- for BKK -> Koh Chang and they offer a "return" ticket (KC -> BKK) for only 300.- baht. But i wonder what time this journey starts at KC and what time the "big bus" will arrive in BKK?

2.) Other option would be to go from Utapao to Phuket. This is also a good option, but i don´t want to pass Pattaya. So does anybody knows if there exists a transfer by Minibus KC -> Utapao`?

3.) Last (and most expensive) is to book a flight TRAT -> BKK -> HKT (Phuket). So for this option: Is there a minibus from KC to TRAT airport and if - how much they charge?