jan ali o, toki!
Don't really know how the things are now, but I read somewhere that there are no tp analogues for please and thank you words, and that it's by design.
Is it really so? If yes, then (in my humble) this needs to be fixed. Rationale in the last paragraph.
I've made up these variants. What do you think about them? I''d like to see yours )
please: sina pana pona la ...
thank you: sina pona.
you are welcome: sina pona kin.
Now on necessity of verbal gratitude. You may well skip the rest of the paragraph, unless you're curious about this quirk of human talk.
I'm translating some behavioral science to my mother tongue and here's the reasoning why those words are necessary to the language. (All credit to B. F. Skinner, who was very clever a man indeed).
There are three kinds of speech, if you divided it by its "reinforcements". To put it simple, they are commands ("I want a candy!"), names for things and events (in a very broad sense, "red" for example, or "on the table") and modifiers to the speech itself (for example "for example"). There are many further subdivisions, but let's look the first type, mands. What makes them different is that they are reinforced by the listener's action, specified in the mand. "Give me a candy" specifies exactly what listener's action will be reinforcing to the speaker.
Now to the point. I know it's long and may seem kinda irrelevant.
In other types of verbal behavior the benefactor is the listener; only mands are for the benefit of the speaker himself.
That's exactly the reason why in every single culture there exist rituals around mands: equivalents of "please", predisposing the listener to act for the speaker, "thank you", which reinforcers listener's cooperation to ensure that he will cooperate again in the future, and "you are welcome", reinforcing that reinforcement.
Hope that makes sense to you as it does to me )
sina pona tawa mi tan ni: sina lukin e sitelen toki ali mi.