Lombok, Indonesia – for a couple of reasons.

Lombok is a laid-back, easy-going beach paradise right next to Bali. It's pretty much like Bali without tonnes of tourists.

You can get really cheap flights to Bali (since so many people go there). Going from Bali to Lombok takes less than a day by bus/taxi and ferry. I ended up near Senggigi, Lombok by coincidence last summer and ended up staying there for weeks. I halfway plan to do what you're doing once and that's probably where I would go. :-)

You will probably not find super-fast Internet connections outside of cities/tourist destinations, but unless you often need to download gigabytes of data that shouldn't be a problem.