I have a simple form with 2 text fields and a search button.
I.e. something like this:
I don't like the checkbox as it is. How could I improve this better?
With no further information this how you can improve your form:
If descending and ascending are for the results then you may want to propose that option afterwards, once the results displayed
The two buttons on the right are supposed to be segmented buttons. :-) They can be used before and after the search.
The sorting of the results should be displayed after the results are shown. Currently, it's not very clear what the context for ascending is or how the results will be sorted - depends on what fields you will display for each result (name, date, type, other metadata); I'm guessing you'll have more than one field given that you have 2 search boxes.
Additionally, maybe you can try and leave only one search field and display the results something like this
and allow the users to sort also by the last column