Hello, i am looking for a non gay sauna that is modern, clean and that preferable allows mixed sexes to use the same sauna.

I don't think saunas in Chiang Mai are classified as "gay" or "non-gay", but I may be wrong about that.

In any event, don't drop the soap.

 Duangtawan Hotel has a health club on the 4th or 5th floor with sauna, steam room facilities, Around 2 or 300 baht for day use.

The House of Male, near the Green Palace Hotel, may be what you want.  Take a try and report back.  

Whoa, seriously bad advice on this thread.  The hotel saunas, like Duangtawan and Shangrila are single-sex saunas in the locker/changing rooms.  Very nice and not gay (at least not the female ones), but not open to the opposite sex.  And House of Male is definitely a gay sauna -- at least that's what I've been told by my gay friends.  These saunas are nice, clean and reasonably priced, however.

 

I think some of the upper-end spas offer private saunas rooms for their "couples" treatments.  You could check with them, but expect to pay accordingly.