My question involves workers compensation law for the state of Massachusetts. The employer is a MA resident.

I worked for a total of 6 weeks, approximately 20 hours a week. My employer promised an hourly wage, and I have an email detailing the promised wage and relevant calculations.

Unfortunately, three weeks after the job was complete, I have not been paid yet; the total amount owed is about $4000 USD. The employer is not responding to my messages regarding the unpaid wages.

What is the best course of action to take?

Potential complications:
Work (teaching job) was completed overseas (employer is US resident).
I do not believe the employer has a registered business entity; possibly operating as sole proprietorship.