They are not easy to come by because they are based on a country quota system. You may also need to do a written test on shrimp farming, water buffalo rearing and poultry raising. Also water management irrigation etc.
I was in a similar situation but with the customs dept when I had to import personal effects into Thailand back in 2012. A fee was paid without receipt and another with receipt.
My advise if you can -front the cash -do it everything has its price.