Depending on the power of the filter, it may not have much suction. My female betta likes to play near hers and it hasn't been a problem (I was worried about it myself).
If you're worried, you can wrap a thin sponge pad around it with a rubber band, so if he does get pulled towards it it won't hurt him. Use the kind of black mesh sponge stuff that is frequently on the back of a filter. It may reduce the flow of your filter some, but it shouldn't totally ruin its ability. I had to do that once for a particular clueless male veiltail I had back in high school who thought the filter in my 10 gallon was great fun to get stuck to. Kinda miss my derpy Watermelon.
You could also give him something up there to rest on as well as to block some of the current on part of it using some fake or real plants that are tall enough to touch the top of the water.
Seraphina - female halfmoon