Can anyone recommend a  "professional translator" to get a couple of documents translated  into English?

 

How much should I expect to pay for translation?

A couple I have used (I think each charge similar approx 500 thb/pg):

1. Star Visa Service near US consulate.

2. Humanities Dept at CMU.

 

Edit: 500 thb / pg

The price for translation services depends on the nature of the documents.  For something very routine, like a Thai death certificate, Star Visa Service near the U.S. Consulate can provide an English translation in a couple hours for well under 500 baht.  For something more complex, like a technical document, then that could be more expensive and time consuming.  It's all a matter of vocabulary and how often the translator deals with similar documents.  A resource list from the U.S. Consulate is a good place to start for leads:

 

https://th.usembassy.gov/wp-content/uploads/sites/90/2016/08/translation-service-providers-chiangmai.pdf