There is no called „eTravel Visa“ for the Philippines. You talking about the eTravel pass (formerly eArrival card). An digital platform to register passenger data for border control etc.. Easy to register by yourself and it’s free of charge.
You can show everything from your mobile device as well. And rental agreement could be just a hotel booking for a few days/ weeks. That’s fine for the IO. He mentioned he was in Thailand soon before, so I guess he still could have a eSIM or SIM card he just needs to switch on.
I guess he knows that exactly. You might got it wrong. After the extension you can stay another 180 days. Then you must leave Thailand and can reenter for a new 180 days, which can be extended also only one time for 180 days. So that’s 360 days (around 12 months) between the 2 extensions, exactly like he described it. Can be also longer depending on how long he’s staying outside of Thailand.