there are no bad choices here. only too many.
Since you've booked to bali, i'd probably do it. I by the way went around bali and I'd recommend the same to you. don't assume you'll stay just in one area. spend a night or two in ubud, maybe one in lovina and one or two on the south coast or some combination of such.
but you could do anything from going to malaysia (penang or borneo) to going to bangkok. there are way too many choices. and by the way, i've done all of these as a solo traveler.