So much misinformation there are legal and legitimate contracts for this. Whilst nominees are illegal. Agents contracts between Thai are completely lawful depending on the company set up.
For legal advice and assistance, I suggest you contact the following who have been assisting overseas nationals since 2007 with smatters
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The British client affairs manager and practising Lawyer together with his in-house team of Thai lawyers bargers and consultants and accountants will guide you through the process legitimately and legally
I hope this assists