Everyone needs a visa, and you will need to get one before you arrive.
Tourist visas need an invitation and can be very expensive to arrange. It is easier and quicker to obtain a transit visa that allegedly can be used for up to seven days with extensions.
You will need to organise the visas for the countries you are transiting from/to before making your application.
Turkmenistan Visa Information
Turkmenistan Migration Service
Turkmenistan embassies
