How to use "Thread" type

Follow the website Thread - API references and tutorials | Mbed OS 6 Documentation
I try to use “Thread” type like examples on website.
But when i work on Online Mbed Simulator and copy the code, the console told me

/out/user_1615893500118.cpp:11:1: error: unknown type name ‘Thread’

i would like to know how to apply “Thread” on Online Mbed Simulator.
Thanks for your help!!!

To enter the Online Simulator, click https://simulator.mbed.com/