It looks like SIMBA plans are setting the trend for telcos to offer free 1 GB of free data roaming to well visited neighbouring countries. Maxx now has a new $15 plan which gives you 70 GB, in addition it is throwing in 2 GB of roaming data to Malaysia, Indonesia and Bangladesh.
One thing to note is that it does not offer any free voice roaming. Thus, when you are overseas, you are have to rely on whatsapp or telegram for calling home.
Seriously, when overseas, it would still be advisable to get a local data voice prepaid sim and use it as SIM2 (irrespective of which local telco you use).