Asylum-seekers, who are still in a procedure to receive international protection have the right to work in Bulgaria 3 months after the date of submission of their applications for international protection. After that you can hire them under the same conditions as Bulgarian citizens.

People with refugee or humanitarian status or people who hold temporary protection have the right to work in Bulgaria under the same conditions as Bulgarian citizens. 

In both cases you, as an employer do not need to obtain special permits to hire asym seekers, people with refugee or humanitarian status or people who hold temporary protection. You are obliged to inform the General Labour Inspectorate that you have hired them within 7 days as of the date on which they started working. You can find the form here - https://bit.ly/3UUCSWZ