If you're from the US, the DTA specifically excludes Social Security and any other governmental (i.e. state or local) pension from taxation by your country of residence. So if your main income is from Social Security and/or a governmental pension, and that's the money you're transferring to Thailand, conceivably you don't owe any taxes in Thailand.
For any US expats, the double-taxation agreement between the US and Thailand specifically says that Social Security, and any other Governmental pension (i.e. State or Local pension) can ONLY be taxed by the United States (see Article 20), therefore Thailand could only potentially tax you on any other income. (and again, under the double-taxation agreement, Thailand Must credit you for any taxes paid to the United States.
A difference without any meaning. Under a double taxation agreement, you can be "taxed" by your country of residence, BUT, you get a credit for any taxes you paid to your original/home country.
I use ultramobile for the same purpose for $10 month (paid yearly), you do need to add a little to activate roaming, but if you don't make any calls it just sits there.
Depends on the source country, some countries (such as the United States) have reciprocal tax treaties with Thailand that prevent double-taxation, so Thailand cannot tax you.
We are unable to guarantee that our numbers will work with phone verification services, such as the kind businesses such as PayPal, eBay and Craigslist use, that allow you to create accounts with other services. We cannot guarantee that our numbers will work or have never been used for the same purpose prior to your purchase, and as such, if we know about the verification service and it has been abused in the past, we will block incoming calls from such services.
We will not issue a refund if you purchase a number with an intent to use such automated account authorization and verification services and it does not succeed, regardless of your legitimacy for using it.