One question would be how old are you and how old is he? What @mauRICE said is true, though I would have worded it less harsh. That you met on Grindr does not make him no moneyboy. Plenty of them are there. And on ThaiFriendly, HeeSay, Hornet, Romeo, etc. Often on all of them.
Also I would advise that what you have is not dating, at least not in the Thai sense. There dating is in phases, like being friends, talking-phase / Khon Khui (คนคุย) which is half official, and then maybe being boyfriends (faen). What you have is a simple hookup - which is not bad at all. But don't confuse it with dating.
Considering your question on faithfulness: Do you really expect him to live like a monk for months, waiting for you? Do you think that would make him happy? Because that should be your goal in a "relationship". Maybe he does not return your affection because he does not feel it, or maybe he protects himself because you would not be the first farang that just disappears after promising all sorts of things. You may want to look up Jai Yen (ใจเย็น) "cool heart".
Best luck to you.