Same as for Koh Jum the boat starts from Leam Kruad pier, see timetable below. Since we already were on Koh Jum, you need to take the boat back to Leam Kruad pier and change boat to reach Sriboya.
Another alternative is to rent a Longtail boat and go directly from Koh Jum to Sriboya. Since we were 10 people it was more economic to rent the Longtail, it cost us 1500thb and saved a lot of time.
We rented bungalows at Siboya Bungalows which was a good decision, very relaxed area. Clean and well-maintained resort. Lots of hammocks to take a nap in and also here a good kitchen and bar.
Compared to Koh Jum there are even less to do on Sriboya, just time to chill out.
We had a great time and will be back.