Scarlet Heart Thailand

It's the first original version of Scarlet Heart written by Tong Hua and it also has a 2nd part
anyone wants to have a idea what the thai adaptation might look like should try this

— Enemies to Lovers + Friends to Lovers
— Amazing writing and directing by P'off
— Sizzling chemistry of OhmNanon

Ever since they were young, Pran and Pat's families had a deep and raging rivalry, trying to one-up each other on everything. This also extended to their sons. Comparing their sons' achievements and merits,—whether it be academic or extracurricular—the two families leave no stone unturned to outshine and gloat in front of the other.

The rivalry was passed down as a family heirloom and the two boys become rivals in turn. Until... they grow tired and become friends. Really good friends. However, because of their families' rivalry, their friendship has to be kept under wraps. And so began a journey of secret friendship... and then perhaps a secret romance?

Written by the same author, reverse harem,
they have many similarities, Scarlet heart and Lost you forever is Tong Hua's best well known novels

It's the korean remake of Scarlet Heart originally written by Tong Hua, anyone wants to know what might the thai adaptation look like can try this one or if anyone liked the thai version should try this

Scarlet Heart Thailand is adapted from the same novel: Bubu Jingxin (Startling by Each Step) by Tong Hua

Both are thai productions that star Tu and Nanon as (part of) the main characters. Nanon plays a love interest for Tu.

Both are thai historical romance shows where the female lead from modern times is transported back to ancient times.
Trying to survive and adapt to this new life,
Love triangle, side couples

Both are GMMTV produced higher budget shows that are adaptations of a very popular story/novel/manga that has also seen a lot of other popular adaptations (among those also a very popular korean one!). Lots of overlap between the cast - especially Tu and Win - two popular actors who play main characters in both.