Truemove H Tourist SIM have a 90 day validity limit, as compared to normal SIM that can have 365 days in advance. So you need to remember to extend more frequently.
If you are willing to pay 1 baht per minute, then why bother with the drama of worrying about using a service such as Localphone? Yes, it's one sixth of the Truemove H price and there is no need to subscribe, even though you can subscribe for as little as US$1 per month.
It's hard to understand why some agonise over such seemingly trivial decisions.
It's definitely more hassle and more expensive to obtain and maintain the Truemove H Tourist SIM.
My advice....Sign up with Localphone using a PC browser and your U.S. SIM. Your U.S. number can appear as your Caller ID when making a call or sending SMS. Then install the application on your phone and sign in.