Interesting tidbit from the BTS part 2. P'Nok said the script originally had only 2 lives but when they submitted it to the Ch3 elders, they were like, it seems unfair for n'ek. And the lakorn does have a karma theme going on. P'Nok agreed once she thought about it too. That a woman who is a generally good person, does good deeds, suffered a lot and has true love, it's unfair that their love never got a fair shot. She didn't want to make the story hopeless so they added the 3rd life.
I did think the old version Luang Raj and Sarapee got off super easy and they didn't really pay for their sins. But this one Raj is already a good guy in the first life so the happy ending makes better sense.