Hi, I'll be alighting at Haikou Airport and I would like to visit Sanya.

The high speed train station is connected with the Domestic Terminal of the airport. It has two main entrances/exits: one is near Gate no. 2, Domestic Departure and the other is outside Gate no. 2, Domestic Arrival Hall. After landing, follow the signages to find the station and buy ticket to Sanya (within 1.5h). Everything can be easy enough.

It seems simple as you have said. Thanks. May I know where can I get SIM cards with data plan? Once I have alighted from sanya station, how do I get to yalong bay? From sanya station, how much does it costs to get there via public or private transports.

Dongdong, there are three phone operators in China: China Mobile, China Unicom, and Chine Telecom. It is suggested you figure out which service can be supported by your phone and then buy the card at the corresponding branch in the city. You can choose a suitable data plan at that time.
You can take bus no. 15 from Sanya Station to Yalong Bay directly in around 2h. I remember the bus fare is CNY2.

Thank you. May I know where can I find out the regulations for haikou international airport ? Am I able to bring my portable battery and extra batteries to haikou?

Dongdong, you are allowed to take 2 portable batteries at most if their power is less than 100Wh.
If the power exceeds 100Wh but is less than 160Wh, you should get the permit of your airline for taking them.

Okay. Thank you! :)