After some tinkering I finally managed to make it work and I am posting the solution in case others might find it useful.
You need to have your SIM card (I use a hk based eSIM) AND a vpn that can tunnel your traffic to the country in which the sim card is registered.
Signup via sms code this way works. Afterwards turn off the vpn so you are using Thai internet and I can then find all the shops via their official @ line ids.
I added the usual suspects (thanks Mac for the diligent work) so am good to go.
a couple of etiquette questions:
Can I expect the masseur in shops like phoenix or 15m to kiss and cum? Or is that something to be negotiated prior, if at all?
what about specific requests like where the…deposit goes?