There as some people who can play complex bass lines and sing at the same time. Iām not one of them. I think itās genetics for those that can. For the rest of us, itās practice until you can, and be aware there will probably (likely) be some parts you canāt play and sing at the same time.
I canāt add much to the tips already offered, but I will say a couple of the things Iāve stumbled into doing is playing a passage and holding a note somewhere in or at the end of the passage to allow me to sing whatever, then continue playing after getting through the phrase. As I hold one note, I prepare to play the next note when I get to a specific word in the lyric phrase.
As you practice, you will likely notice places you can hold a note, and also places you can play the next note on a specific word in a lyric phrase.
In other words, you can help keep your playing timing and singing cadence when you can find places they rest and places they cross paths. As I said, you will find these moments as you practice & when you do, you can repeat them until they become comfortable and automatic.