When you say you have a Google Nexus... do you actually mean you use Google Project Fi on your device and plan on using that while in Thailand and Bali?
Anyway, Tourist sim cards are cheap and readily available in both Thailand and Indonesia. You can put those in your unlocked phone or tablet and viola hotspot (yes they allow tethering). Coverage is very good and speeds are excellent (most places, certainly around CM and most of Bali... 10-20Mbps on average, sometimes more sometimes less).
Cafe WiFi in Chaing Mai is usually very good.
Cafe WiFi in Bali is usually pretty poor*.
- Personally I tethered to my own hotspot (Ipad with TelkomSel SimPATI Sim) more often in Bali at cafes than I relied on their flaky WiFi.
CoWorking spaces (yes I know you said you weren't going to them) are excellent in CM and Bali, some of the best anywhere in the world IMHO. If you didn't at least visit PunSpace and Hubud fora day or two you'd be doing yourself a disservice.
To your specific question (if you can't/don't want to pop a sim in an existing device) then in Indonesia at least I'd recommend a hotspot device if your own.
Personally I have T-mobile (US) on my iPhone and kept that active globally, then I pop a data sim in my iPad for tethering... or on occasion swap sims back and forth in the iPhone.
Bonus: In Thailand if you get a True or AIS sim card is they often come with free public wifi which is pretty plentiful in major areas... DTAC less so... but has better coverage some places in the south.
I don't recall public wifi tied to TelkomSel/SimPati cards in Indonesia on Bali or elsewhere... but maybe it's a thing though... certainly not plentiful like True/AIS wifi spots in CM/BKK.