I need to know how much extra costs would be involved if a company had to make one more Thai employee legal.How much tax/extra costs would the company have to pay if he/she earns 5200 Baht.

any information is welcome.

I beleive there is no income tax to pay on 5200 baht though 7% social security could be applicable

Ask your accountant.

Normally 10% (5% paid by employee), so cost to the employer would be 5% (260 per month).

However there was a recently a tax break i can't remember if it's still on where it was reduced to i think 6% (so only 3% paid by employer), but that may have already expired.