If didn't threaten job or intimidate in any way, would it be sexual assault?

Yes, if told NO. Sexual assault is defined by a lack of permission/consent by either party(male or female) to engage in any form of sexual activity. It doesn't matter whether it is job related, or you say "pretty please" the judicial system considers it non-permissable and prosecutes the "act".
? intimidate ? Beauty or intimidation is a value judgement in the eye of the person viewing the issue.What you believe about threat or intimidation is irrelevant.If you are a boss and contemplate any non professional activity with an employee, you are automatically in a dangerous situation. The adage "don't fish in your own backyard" comes to mind.