I would like to add a select field like a drop-down in the contact form to let user select the reason why they contact (contact, customer support, etc.)
Based on this (excellent) answer Adding check boxes to contact form, i’ve managed to create a field with check box :
source : Adding check boxes to contact form
How can i do that with a select ?
You can choose in the "manage form display". The column "widget" allow to choose "Select list" (see screenshot)