I’m looking at an option to be able to make and receive calls without a SIM card. I used to have a Skype phone number a long time ago. No longer a Skype user, I am looking at a non invasive android alternative. This should be a solution that is available in Thailand and suitable for personal use. (I have found a couple of solutions online for the US and business).
There are various solutions out there. Here just 2 that I know:
Localphone.com - They offer various VOIP features, one if them is an incoming number. All services are pretty fairly priced.
The other one is called Satellite.me, it is an incoming and outgoing full-featured phone number that is not SIM based but app based. 2 downsides: It is a Germany-based company, so out of the box you get a free German landline number but I think you could add-on other ones by now. And the other one is that the app requires Google Play Services and currently does not work with /e/ - unfortunately.
What about a straight SIP provider like voip.ms? You can add a SIP account in the native /e/ dialer app under settings, so it would behave like a normal phone with the standard dialer.