The accident happened on Highway 41 in Surat Thani at 05.22 am today.
Highway police said the bus with 17 foreign tourists was on the way to Krabi province after leaving Bangkok yesterday evening.
It was raining heavily as the bus was approaching Km 118 on Highway 41
It skidded while making a curve, flipped over and overturned to the roadside bushes.
Fifteen tourists were injured, one of them trapped inside the overturned bus.
Rescue team arrived at the scene after being alerted, and quickly rushed all the injured to Thachana hospital.
Two others were unscathed.