One of the biggest things farangs will encounter is the frustration of their helpfulness / kindness not being returned in kind. They will give, but then get frustrated when the receiving person doesn't seem to give a shit, and kindly goes on with their life as if nothing happened.
If you settle in to Thailand though, you will realize, this is just the way things are done here. You will notice as long as you're a decent individual, many people will do you favors for no reason. Small favors, but nonetheless, they go out of their way for you. If you ever try to repay them instantly for their kindness, there's a good chance they will be offended, and completely refuse. However, if later on in the future you decide to do them a favor, they will humbly accept it, and thank you for it.
It's just the way things work here. You help people because you have a good heart, and want to reach Nirvana, basically. Accepting a return on that helps defeat the purpose, hence most Thais will get offended if you offer instant reprisal. Instead, you humbly take what's given to you, help where you can, but never expect anything in return. That's just the way it works here, so when you help someone and think to yourself, "what an unappreciative asshole!", then that's why.
This is also how you can tell someone is genuinely Buddhist. Offer them help, and if you can tell they feel disrespected by the offer, then that helps let you know they're genuine.