These two dramas are Thai BL drama. Both drama show a few similar storyline. For instance, one character likes the other character but it is unrequited love until that character tries many possible ways to make the love happens!
Pee Nak 2 is based only movie Pee Nak with some original characters. Pee Nak 2 explores more into the stories of previous characters in Pee Nak.
SaifahZon Story is originated from Why R U the Series. The characters of Saifah and Zon were already in that series and their love story began in Why R U the Series. Anyone who finds SaifahZon Story but never watched Why R U should watch Why R U first to better understand their love journey.
Theory of Love: Special Episode "Stand By Me" has a parent story called Theory of Love. This parent story tells how Khai and Third started dating and also the friendship of this four gentlemen: Khai, Third, Two and Bone. Theory of Love's story revolved around how these four friends life during study time but ToL: Special Episode "Stand By Me" is a story after they finished the study. If by chance some audiences found this one-hour special episode and haven't watched the original parent story, they should watch Theory of Love first to understand more about the storyline.