May I know where can I buy prepaid sim card in Shantou for mobile phone?

You can buy prepaid sim cards at the branchs of China Mobile. You may go to the branch at No. 103-104, Jindong Garden, No. 90, Dongxia Road.
1). You need to pay around CNY 50-100.
2). Yes, it can be used in Xiamen. But you may use the GSM service to save money. :)

Thanks for your reply.

1) For the prepaid sim card, is it available at the jieyang airport?

2) I will be staying at Junhua Haiyi hotel,
2a) how far from hotel to go to Jindong garden or from hotel to Dongxia road?
2b) By what transport?
3) Are there other China Mobile near my hotel (Junhua Haiyi Hotel) area?

1). The sim cards are available at the airport, but I am not sure of its exact location. You may consult the staff at the Inquiry Desk.
2). It is about 1.1 miles (1.8km) from the hotel. You may take bus line 31 from the hotel to Jinping District People's Hospital (Jinpingqu Renmin Yiyuan) Station. Then, walk north for about 500 yards to the branch.
3). Yes, you may go to the branch at No. 43, Juyuan, Jinping District. Walk south along Jinhuan Road for about 200 yards, and turn right. Walk southwest along Longhua Street for about 300 yards to the branch.