a Chef is a Chef wherever he is his value & education is at the top so wage I wrote is the VERY minimum & can be even 150.000 bahts but do not worry such Chef will never come to work in thailand.
as you are a thai it will be easier, make a visit to the immigration services, ask them all the documents you need to hire a foreigner chef for your rest.
For the foreign side if he has the qualifications needed for the business you offer i think there won't have problem. Just wait wait at the queue. lol
ow i forgot, make a visit to the labour dep. to get all documents needed too for the WP.