[wolfbln]

Hi. I'd like to give a short review of the AIS SIM2Fly SIM from my Asian travels in Feb/March 2019.
I bought it in Thailand where they heavily market it at the airports and in AIS stores. The Asian starter is for THB 899 (that's about $12.5 or €11). It comes with 4GB for 8 days.
The clock really starts when you first connect to a non-Thai roaming network or more specific establish a data connection through it. There are topup packages slightly cheaper available.

First stop was AUSTRALIA. Here I got a big disappointment. While they use the best network Telstra in 4G, obviously it's on a very unfavorable routing. It gave me a latency of 400ms and more on LTE making VoIP calls and good surfing almost impossible.
Next stop was INDONESIA: much better, again on the best network in the country called Telkomsel in 4G and good speed and latency.
Third stop MALAYSIA and here they sell special discounted packages for "neigbouring" countries. You can add more packages and activate them through an USSD-code also in roaming. Network was Cellcom in 4G.
At my final stop SINGAPORE I had all three networks in 4G at good speeds.

So it's a good option for SE Asia, especially when you start in Thailand. I know this SIM is marketed in the whole region, but outside Thailand rather at a premium which may make it more expensive than other options.
Still, the local SIM options are cheaper, but if you only stay for short or use only 1-2 GB, it's not worth buying new SIM cards in every country. Indonesia has hiked the prices for new SIMs since the introduced mandatory registration last year and many other countries register as well.

Further off the area things get more mixed: latency turns very bad and off the Asia-Pacific area data is rather expensive at more than €6 or $7 per GB in Europe or the US.

A big problem remains: this SIM card is a Thai SIM governed by the Thai top-up rules. Every top-up extends SIM validity by only 30 days. This makes it very hard to keep it for a long time. Furthermore, there are no surcharge-free top-up options outside Thailand as the AIS website doesn't accept foreign credit cards (they don't tell, but that's like it is) leaving mobiletopup.com as the cheapest option with a 5% surcharge.

Summing up, it's a good option for SE Asia travels not only for Thais, but everybody who is cruising around this area, but I wouldn't take it to other regions and you can't keep it alive, if you visit the area only once a year.