The strong points of the series are Bright's musical scenes, reasonably three dimensional performances from the leads, and the soundtrack. The weak points are unconvincing body language between the leads and some clumsy writing that makes the series drag in places.
The main arc and plot is well supported by the performances and soundtrack: an introvert who has a habit of communicating emotions through music meets and falls in love with somoene with whom that resonates, and the two of them need to work out how to make the sometimes awkward relationship work. For the series to work the musical scenes need to work, and Bright is a good enough musician to pull that off. The scenes where he sings to Tine are convincingly touching and carry the emotional impact they need to.
What doesn't work so well is the body language between Sarawat and Tine. They just don't seem to be a couple in love very often. I suspect it's in part intentional: a somewhat awkward relationship with an introvert that is somehow advanced by sharing emotions through music. I think it's probably also a result of having limited time to work on multiple takes of the secenes where they interact privately because of the time it likely took to shoot the musical scenes in the series.
Overall though I think the series accomplishes most of what it aims to do, and it's one of the best music centered series I've seen. If they had resorted to the usual fake guitar and produced vocals the series would have been a failure. Very credible and raw musical performances are worth the tradeoff of a little less credible chemistry between the leads here and there.