This is about a guy running into an old flame after a significant amount of time has passed. After some brief pleasantries, he mentions the loving words she said to him and the sting he still feels knowing she has said them to another guy. And he reminds her that she will regret losing him.
It is a bit unusual and challenging, when the past invades the present. I guess it depends on the individual, how they will react to the encounter. Willie Nelson wrote it, and he sings it like he would, cordial and friendly, twinkly, matter-of-factly, no hard feelings. Al stretches and twists his words, like each one contains multiple meanings. Is he really doing fine? Or is he sarcastic, tired, disgusted, amused, lecturing? Willie sounds like he's standing in the doorway of a farmhouse, thinking it's a nice day outside, whereas Al is relaxing in a dark lounge at two in the afternoon, bourbon in his hand. He's like, don't worry, I've got this. When he sings "remember what I told you, that in time you're gonna pay", that's the one that he sticks her with, sends her off in tears.
At 3:43, there's noticeable reverb when Al sings "in time". What's up with that?